This document provides instructions and questions for a final examination in electromagnetic field theory. It consists of 5 questions testing concepts such as electric and magnetic fields, Maxwell's equations, boundary conditions, wave propagation, and vector calculus identities. The examination is for a course taught in the 2009/2010 semester and covers topics including electrostatics, magnetostatics, and time-varying fields. Students have 2 hours and 30 minutes to answer 4 out of the 5 questions.
IRJET- Thermomagnetic-Gravitational Convection in a Vertical Layer of Fer...IRJET Journal
This document summarizes research on thermomagnetic-gravitational convection in a vertical layer of ferrofluid between two differentially heated plates in an applied magnetic field. It investigates the linear stability of the system for varying governing parameters. Three main types of instability patterns are observed corresponding to thermo-gravitational, magnetic, and magneto-gravitational convection. An oblique external magnetic field introduces asymmetry and qualitatively changes stability characteristics compared to a normal field case, preferentially shifting instability structures toward the hot wall. For each field inclination angle, there exists an orientation angle that most promotes magneto-gravitational instability onset. Dimensionless governing equations are derived and linearized perturbation equations in normal mode
IRJET- Thermomagnetic-Gravitational Convection in a Vertical Layer of Ferrofl...IRJET Journal
This document summarizes research on thermomagnetic-gravitational convection in a vertical layer of ferrofluid between two differentially heated plates in an applied magnetic field. It investigates the linear stability of the system for varying governing parameters. Three main types of instability patterns are observed corresponding to thermo-gravitational, magnetic, and magneto-gravitational convection. An oblique external magnetic field introduces asymmetry and qualitatively changes stability characteristics compared to a normal field case, preferentially shifting instability structures toward the hot wall. For each field inclination angle, there exists an orientation angle that most promotes magneto-gravitational instability onset. Dimensionless governing equations are derived and linearized perturbation equations in normal mode
The document discusses magnetic properties and their temperature dependence. It describes how saturation magnetization decreases with increasing temperature and disappears at the Curie point, above which materials become paramagnetic. It also discusses magnetic domains and how they form to minimize demagnetization fields. Hysteresis loops are described for soft and hard magnets, and their different applications and optimization. Superconductivity is introduced, noting the Meissner effect and resistance dropping to zero below the critical temperature.
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Microstructure and properties of high temperature superconductorsSpringer
The document discusses type-II superconductors and high-temperature cuprate superconductors.
1) Type-II superconductors allow magnetic field penetration in the form of quantized flux lines called vortices above a lower critical field Hc1. Between Hc1 and an upper critical field Hc2, the material is in a mixed state containing a lattice of vortices.
2) High-temperature cuprate superconductors require doping to introduce charge carriers. Their superconducting phase occurs between 5-27% doping and peaks at around 16% doping, in contrast to monotonic behavior in conventional superconductors. Doping introduces charge inhomogeneity through charge stripes that
Study of Boron Based Superconductivity and Effect of High Temperature Cuprate...IOSR Journals
This paper illustrates the main normal and Boron superconducting state temperature properties of magnesium diboride, a substance known since early 1950's, but lately graded to be superconductive at a remarkably high critical temperature Tc=40K for a binary synthesis. What makes MgB2 so special? Its high Tc, simple crystal construction, large coherence lengths, high serious current densities and fields, lucidity of surface boundaries to current promises that MgB2 will be a good material for both large scale applications and electronic devices. Throughout the last seven month, MgB2 has been fabricated in various shape, bulk, single crystals, thin films, ribbons and wires. The largest critical current densities >10MA/cm2 and critical fields 40T are achieved for thin films. The anisotropy attribution inferred from upper critical field measurements is still to be resolved, a wide range of values being reported, γ = 1.2 ÷ 9. Also there is no consensus about the existence of a single anisotropic or double energy cavity. One central issue is whether or not MgB2 represents a new class of superconductors, being the tip of an iceberg that waits to be discovered. Until now MgB2 holds the record of the highest Tc among simple binary synthesis. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search for superconductivity in related materials, several synthesis being already announced to become superconductive: TaB2, BeB2.75, C-S composites, and the elemental B under pressure.
- In ferromagnetic materials like iron, magnetic domains align with an applied magnetic field, causing domains favorably oriented to grow at the expense of unfavorably oriented domains.
- Materials respond differently to magnetic fields based on their properties, including diamagnetism, paramagnetism, ferromagnetism, antiferromagnetism, and ferrimagnetism.
- Hysteresis curves relate the magnetic flux density B and magnetic field strength H for ferromagnetic materials, exhibiting properties like saturation magnetization, remanence, and coercivity.
This document provides instructions and questions for a final examination in electromagnetic field theory. It consists of 5 questions testing concepts such as electric and magnetic fields, Maxwell's equations, boundary conditions, wave propagation, and vector calculus identities. The examination is for a course taught in the 2009/2010 semester and covers topics including electrostatics, magnetostatics, and time-varying fields. Students have 2 hours and 30 minutes to answer 4 out of the 5 questions.
IRJET- Thermomagnetic-Gravitational Convection in a Vertical Layer of Fer...IRJET Journal
This document summarizes research on thermomagnetic-gravitational convection in a vertical layer of ferrofluid between two differentially heated plates in an applied magnetic field. It investigates the linear stability of the system for varying governing parameters. Three main types of instability patterns are observed corresponding to thermo-gravitational, magnetic, and magneto-gravitational convection. An oblique external magnetic field introduces asymmetry and qualitatively changes stability characteristics compared to a normal field case, preferentially shifting instability structures toward the hot wall. For each field inclination angle, there exists an orientation angle that most promotes magneto-gravitational instability onset. Dimensionless governing equations are derived and linearized perturbation equations in normal mode
IRJET- Thermomagnetic-Gravitational Convection in a Vertical Layer of Ferrofl...IRJET Journal
This document summarizes research on thermomagnetic-gravitational convection in a vertical layer of ferrofluid between two differentially heated plates in an applied magnetic field. It investigates the linear stability of the system for varying governing parameters. Three main types of instability patterns are observed corresponding to thermo-gravitational, magnetic, and magneto-gravitational convection. An oblique external magnetic field introduces asymmetry and qualitatively changes stability characteristics compared to a normal field case, preferentially shifting instability structures toward the hot wall. For each field inclination angle, there exists an orientation angle that most promotes magneto-gravitational instability onset. Dimensionless governing equations are derived and linearized perturbation equations in normal mode
The document discusses magnetic properties and their temperature dependence. It describes how saturation magnetization decreases with increasing temperature and disappears at the Curie point, above which materials become paramagnetic. It also discusses magnetic domains and how they form to minimize demagnetization fields. Hysteresis loops are described for soft and hard magnets, and their different applications and optimization. Superconductivity is introduced, noting the Meissner effect and resistance dropping to zero below the critical temperature.
Magnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materialsMagnetic properties of materials
Microstructure and properties of high temperature superconductorsSpringer
The document discusses type-II superconductors and high-temperature cuprate superconductors.
1) Type-II superconductors allow magnetic field penetration in the form of quantized flux lines called vortices above a lower critical field Hc1. Between Hc1 and an upper critical field Hc2, the material is in a mixed state containing a lattice of vortices.
2) High-temperature cuprate superconductors require doping to introduce charge carriers. Their superconducting phase occurs between 5-27% doping and peaks at around 16% doping, in contrast to monotonic behavior in conventional superconductors. Doping introduces charge inhomogeneity through charge stripes that
Study of Boron Based Superconductivity and Effect of High Temperature Cuprate...IOSR Journals
This paper illustrates the main normal and Boron superconducting state temperature properties of magnesium diboride, a substance known since early 1950's, but lately graded to be superconductive at a remarkably high critical temperature Tc=40K for a binary synthesis. What makes MgB2 so special? Its high Tc, simple crystal construction, large coherence lengths, high serious current densities and fields, lucidity of surface boundaries to current promises that MgB2 will be a good material for both large scale applications and electronic devices. Throughout the last seven month, MgB2 has been fabricated in various shape, bulk, single crystals, thin films, ribbons and wires. The largest critical current densities >10MA/cm2 and critical fields 40T are achieved for thin films. The anisotropy attribution inferred from upper critical field measurements is still to be resolved, a wide range of values being reported, γ = 1.2 ÷ 9. Also there is no consensus about the existence of a single anisotropic or double energy cavity. One central issue is whether or not MgB2 represents a new class of superconductors, being the tip of an iceberg that waits to be discovered. Until now MgB2 holds the record of the highest Tc among simple binary synthesis. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search for superconductivity in related materials, several synthesis being already announced to become superconductive: TaB2, BeB2.75, C-S composites, and the elemental B under pressure.
- In ferromagnetic materials like iron, magnetic domains align with an applied magnetic field, causing domains favorably oriented to grow at the expense of unfavorably oriented domains.
- Materials respond differently to magnetic fields based on their properties, including diamagnetism, paramagnetism, ferromagnetism, antiferromagnetism, and ferrimagnetism.
- Hysteresis curves relate the magnetic flux density B and magnetic field strength H for ferromagnetic materials, exhibiting properties like saturation magnetization, remanence, and coercivity.
This document describes how to study the B-H curve of materials using an oscilloscope (CRO). It discusses the apparatus needed including a B-H curve cabinet, transformer, sample coil, CRO and other components. The aim is to trace and study the B-H loop of ferromagnetic materials. The document provides background on magnetism, different types of magnetic materials like diamagnetic, paramagnetic and ferromagnetic, and concepts like domains, Curie temperature and hysteresis. It outlines the procedure to connect the components and record the hysteresis loop on tracing paper to analyze properties like retentivity and coercivity. Potential applications are also mentioned like in magnetic tapes, hard disks and credit cards.
This document discusses a fusion-driven rocket (FDR) concept for rapid interplanetary travel. It summarizes the FDR approach, which uses magneto-inertial fusion to directly convert fusion energy into propulsive energy through a thick metal blanket and magnetic nozzle. Initial mission studies show the FDR could enable 30-day and 90-day missions to Mars, with the 30-day option providing the fastest transit but lower payload mass fraction, while the 90-day option allows higher payload but a longer trip. Further development is needed to advance the FDR concept to a technology readiness level of 5 through experiments and additional mission analysis.
This document describes an experiment to test the hypothesis that increasing the specific surface area of projectiles in a coilgun will increase the net magnetic force and resulting kinetic energy imparted. Four iron projectiles with varying surface areas but identical masses were 3D printed and fired through a two-coil 110 kA/m coilgun. Motion analysis was used to measure the distance traveled by each projectile, from which the work done by magnetic forces could be calculated using a friction model. The results would show either a linear relationship between distance traveled and specific surface area, validating the hypothesis, or no relationship, invalidating it.
Research Inventy : International Journal of Engineering and Science is publis...researchinventy
This document summarizes research on characterizing the electrical properties of AlGaN/GaN modulation-doped field-effect transistors (MODFETs). Key findings include:
- A threshold voltage of -3.87V, maximum saturation current of 122.748 mA, and transconductance values were achieved.
- Dependence of two-dimensional electron gas density at the interface on Al mole fraction and AlGaN barrier layer thickness was presented.
- A novel method for studying AlGaN/GaN interface properties by solving the Schrodinger and Poisson equations self-consistently using finite difference methods was developed. This allows calculating electron distributions, energy band structures, and other characteristics of
The document describes a new thermoelectric converter called the MDSM (Metal-Dielectric-Semiconductor-Metal) converter invented by Gevork Karapet'yan. It consists of a capacitor with a thermoelectric junction that can efficiently convert thermal energy to electric energy. Research showed that applying a magnetic field can change the thermoelectric force in Indium antimonide by 7 times, potentially improving generator efficiency. The proposed MDSM converter uses an electric field rather than magnetic field to vary the thermoelectric force. It could be used to build more efficient thermoelectric coolers and generators by reducing parasitic heat flows and electric losses. Applications mentioned include powering wearable sensor nodes from body heat.
Chiral Transverse Electromagnetic Waves with E H i to study Circular Dichroisminventionjournals
It is shown that a general class of transverse electromagnetic waves with E H i can be obtained. These waves possess magnetic helicity and chirality. This condition is important to excitation of nano molecules when it is necessary consider a global factor as the product of the parameter of optical chirality with the inherent enantiometric properties of the material. The absorption of a chiral molecule in a chiral electromagnetic field is proportional to the imaginary part of mixed electric-magnetic dipole polarizability of the molecules, which determines the circular dichroism, CD of molecules. Chiral fields with different handedness can be used to obtain basic information from the interaction fields-molecules with high optical chirality, having chiral hot spots in nodes of stationary waves with parallel components of electric and magnetic fields.
This document discusses molecular bonding, energy states of molecules, bonding in solids, and electrical properties of materials. It begins by explaining different types of molecular bonding mechanisms including ionic, covalent, van der Waals, and hydrogen bonding. It then discusses the energy states and spectra of molecules, including rotational, vibrational, and electronic transitions. The document next summarizes bonding in ionic solids, covalent solids, and metallic solids. It concludes by covering electrical conduction in metals, insulators, and semiconductors, as well as properties and applications of superconductivity.
1) Permanent magnetic dipoles in matter originate from unpaired electrons in atoms. The magnetic moment of electrons is expressed in Bohr magnetons.
2) In solids, overlapping atomic orbitals can reduce magnetic moments. For example, Fe has a moment of 4 Bohr magnetons individually but 2.2 in crystal form due to orbital overlap.
3) Materials exhibit paramagnetism, diamagnetism, ferromagnetism or ferrimagnetism depending on their electron configuration. Ferromagnetic materials have spontaneous magnetization above their Curie temperature due to positive exchange energy between atomic spins.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitr...CrimsonPublishersRDMS
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitrogen by Majid Monajjemi* in Crimson Publishers: Peer Reviewed Material Science Journals
The effect of magnetic field direction on thermoelectric and thermomagnetic c...Muhammid Al-Baghdadi
This document investigates the effect of magnetic field direction on thermoelectric and thermomagnetic coefficients of undoped single crystalline InSb at room temperature. It describes how samples of InSb were tested under varying magnetic fields and temperature gradients to measure the Seebeck and Nernst coefficients. The results showed that the Seebeck coefficient depended only on the temperature gradient, while the Nernst coefficient depended on both the temperature gradient and magnetic field. However, the values of the thermoelectric and thermomagnetic coefficients were found to be independent of the direction of the applied magnetic field with respect to the InSb sample surface.
5164 2015 YRen Two-Dimensional Field Effect TransistorsYi Ren
This document provides an introduction to two-dimensional field effect transistors (2D FETs). It first discusses the limitations of conventional FETs as their size is reduced according to Moore's Law. 2D FETs are proposed as a way to continue increasing transistor density by using atomically thin 2D materials as the channel layer. The document then discusses properties of graphene and transition metal dichalcogenides, which are common materials used in 2D FET channels. Finally, examples of 2D FETs using MoS2 and other materials as the channel layer are described.
Thermodynamics of magnetic refrigeration cycles are discussed. Key points:
1. Magnetic refrigeration uses the magnetocaloric effect where applying/removing a magnetic field causes materials to heat up/cool down.
2. Cyclic magnetic refrigeration processes are analyzed using thermodynamic potentials and the first law of thermodynamics. Formulas for work, heat, enthalpy and entropy are presented.
3. Common thermodynamic cycles for magnetic refrigeration like Brayton, Ericsson and Carnot cycles are examined. Cascade and regeneration principles can be applied to widen the achievable temperature range.
domain theory hysteresis loop and magnetioresistance.pptxKiruthikaKiruthi12
This document discusses domain theory of ferromagnetism and its applications in soft and hard magnetic materials. It explains that ferromagnetic materials are divided into small regions called domains, where magnetic moments are aligned in the same direction within each domain but vary between domains, resulting in zero net magnetization. When an external magnetic field is applied, the domains rotate or the domain walls move to align with the field. This causes hysteresis, as explained by the hysteresis loop. Soft magnetic materials have low coercivity and hysteresis losses, making them easily magnetized and demagnetized, while hard magnetic materials have high coercivity and retain magnetization, making them suitable for permanent magnets. Common soft magnetic materials include transformer steel and in
Electron Beam Machining (Modern ManufacturingProcess)Dinesh Panchal
The document summarizes electron beam machining (EBM). EBM uses a focused beam of high-energy electrons to melt and vaporize metal, allowing for precise machining. There are two types - thermal EBM uses the beam's heat to selectively vaporize material, while non-thermal EBM causes surface chemical reactions. The document discusses the generation and control of electron beams, the physical processes involved in thermal EBM, and a phenomenological theory of non-thermal EBM film growth proposed by Christly.
201606_Ferrites,_CMC,_and_Power_Transformer_(1)eRay Lai
The document discusses soft ferrite specifications for CMCs, power chokes, and transformers. It begins by explaining the importance but also limitations of the B-H curve as a characterization of ferrite materials. Key specifications discussed include permeability, saturation flux density, core loss density, and effective bandwidth. However, the document notes that permeability is nonlinear and dependent on factors like temperature, frequency, and load/current. Real applications also involve more complex geometries compared to an idealized toroid shape. Overall, both material properties from the B-H curve as well as mechanical design aspects are important for magnetic component design.
Toru Hara proposes developing an "ultimate energy storage device" with both high energy density like a battery and high power density like a supercapacitor. Specifically, Hara aims to develop a mono-atomic layer FeOOH/NiOOH battery using 3D interpenetrated electrode architectures deposited on graphene paper current collectors to enable efficient ion and electron transport for high performance. If successful, this battery could offer long cycle life by avoiding phase changes during charge/discharge that can destroy crystal structures in conventional battery materials.
Magnetostatic Surface Waves in a Left Handed / Ferrite/ Metal-Strip-Grating ...ijrap
The dispersion characteristics for magnetostatic surface waves in a left handed ( LHM)/ferrite/ metal-stripgrating structure have been investigated. We found that, the waveguide supports backward TE waves
since both permittivity and magnetic permeability of LHM are negative. We also illustrated the
dependence of wave frequency on the reduced wave number for a grating shielding parameter, g values
restricted by the range 0 ≤ g ≥ 1. It is shown that the grating shielding parameter, g induces
magnetostatic backward shorter waves . The leakage through the grating increases with the wave number.
The shorter backward magnetostatic waves are guided by the thicker waveguide where the best
confinement is achieved .
The Free Energy Secrets of Cold ElectricityNOMADPOWER
The phenomenon of consumer devices becoming cold as they consume power is a sign that "Cold Electricity" is powering a consuming device. In terms of its form, "Cold Electricity" also has a voltage supply that produces the same current as a conventional power source. Conventional power from the grid generates work on consuming devices and at the same time gives off heat. But with a Cold Electricity supply, the power-consuming loads tend to absorb the temperature in the environment, meaning they do not emit heat but, on the contrary, collect heat, i.e., get cold during operation.
An Experimental Study on the Migration of Pb in the Groundwater Table Fluctua...NOMADPOWER
As a result of fluctuations in the shallow groundwater table, hydrodynamic conditions change alongside environmental conditions and hydrogeochemical processes to affect pollutant migration. The study aimed to investigate the migration, adsorption, and desorption characteristics of Pb on fine, medium, and coarse sand in the water table fluctuation zone by using several laboratory methods, including the kinetic aspects of Pb2+ adsorption/desorption and water table fluctuation experiments.
This document describes how to study the B-H curve of materials using an oscilloscope (CRO). It discusses the apparatus needed including a B-H curve cabinet, transformer, sample coil, CRO and other components. The aim is to trace and study the B-H loop of ferromagnetic materials. The document provides background on magnetism, different types of magnetic materials like diamagnetic, paramagnetic and ferromagnetic, and concepts like domains, Curie temperature and hysteresis. It outlines the procedure to connect the components and record the hysteresis loop on tracing paper to analyze properties like retentivity and coercivity. Potential applications are also mentioned like in magnetic tapes, hard disks and credit cards.
This document discusses a fusion-driven rocket (FDR) concept for rapid interplanetary travel. It summarizes the FDR approach, which uses magneto-inertial fusion to directly convert fusion energy into propulsive energy through a thick metal blanket and magnetic nozzle. Initial mission studies show the FDR could enable 30-day and 90-day missions to Mars, with the 30-day option providing the fastest transit but lower payload mass fraction, while the 90-day option allows higher payload but a longer trip. Further development is needed to advance the FDR concept to a technology readiness level of 5 through experiments and additional mission analysis.
This document describes an experiment to test the hypothesis that increasing the specific surface area of projectiles in a coilgun will increase the net magnetic force and resulting kinetic energy imparted. Four iron projectiles with varying surface areas but identical masses were 3D printed and fired through a two-coil 110 kA/m coilgun. Motion analysis was used to measure the distance traveled by each projectile, from which the work done by magnetic forces could be calculated using a friction model. The results would show either a linear relationship between distance traveled and specific surface area, validating the hypothesis, or no relationship, invalidating it.
Research Inventy : International Journal of Engineering and Science is publis...researchinventy
This document summarizes research on characterizing the electrical properties of AlGaN/GaN modulation-doped field-effect transistors (MODFETs). Key findings include:
- A threshold voltage of -3.87V, maximum saturation current of 122.748 mA, and transconductance values were achieved.
- Dependence of two-dimensional electron gas density at the interface on Al mole fraction and AlGaN barrier layer thickness was presented.
- A novel method for studying AlGaN/GaN interface properties by solving the Schrodinger and Poisson equations self-consistently using finite difference methods was developed. This allows calculating electron distributions, energy band structures, and other characteristics of
The document describes a new thermoelectric converter called the MDSM (Metal-Dielectric-Semiconductor-Metal) converter invented by Gevork Karapet'yan. It consists of a capacitor with a thermoelectric junction that can efficiently convert thermal energy to electric energy. Research showed that applying a magnetic field can change the thermoelectric force in Indium antimonide by 7 times, potentially improving generator efficiency. The proposed MDSM converter uses an electric field rather than magnetic field to vary the thermoelectric force. It could be used to build more efficient thermoelectric coolers and generators by reducing parasitic heat flows and electric losses. Applications mentioned include powering wearable sensor nodes from body heat.
Chiral Transverse Electromagnetic Waves with E H i to study Circular Dichroisminventionjournals
It is shown that a general class of transverse electromagnetic waves with E H i can be obtained. These waves possess magnetic helicity and chirality. This condition is important to excitation of nano molecules when it is necessary consider a global factor as the product of the parameter of optical chirality with the inherent enantiometric properties of the material. The absorption of a chiral molecule in a chiral electromagnetic field is proportional to the imaginary part of mixed electric-magnetic dipole polarizability of the molecules, which determines the circular dichroism, CD of molecules. Chiral fields with different handedness can be used to obtain basic information from the interaction fields-molecules with high optical chirality, having chiral hot spots in nodes of stationary waves with parallel components of electric and magnetic fields.
This document discusses molecular bonding, energy states of molecules, bonding in solids, and electrical properties of materials. It begins by explaining different types of molecular bonding mechanisms including ionic, covalent, van der Waals, and hydrogen bonding. It then discusses the energy states and spectra of molecules, including rotational, vibrational, and electronic transitions. The document next summarizes bonding in ionic solids, covalent solids, and metallic solids. It concludes by covering electrical conduction in metals, insulators, and semiconductors, as well as properties and applications of superconductivity.
1) Permanent magnetic dipoles in matter originate from unpaired electrons in atoms. The magnetic moment of electrons is expressed in Bohr magnetons.
2) In solids, overlapping atomic orbitals can reduce magnetic moments. For example, Fe has a moment of 4 Bohr magnetons individually but 2.2 in crystal form due to orbital overlap.
3) Materials exhibit paramagnetism, diamagnetism, ferromagnetism or ferrimagnetism depending on their electron configuration. Ferromagnetic materials have spontaneous magnetization above their Curie temperature due to positive exchange energy between atomic spins.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitr...CrimsonPublishersRDMS
A Nano Capacitor Including Graphene Layers Composed with Doped Boron and Nitrogen by Majid Monajjemi* in Crimson Publishers: Peer Reviewed Material Science Journals
The effect of magnetic field direction on thermoelectric and thermomagnetic c...Muhammid Al-Baghdadi
This document investigates the effect of magnetic field direction on thermoelectric and thermomagnetic coefficients of undoped single crystalline InSb at room temperature. It describes how samples of InSb were tested under varying magnetic fields and temperature gradients to measure the Seebeck and Nernst coefficients. The results showed that the Seebeck coefficient depended only on the temperature gradient, while the Nernst coefficient depended on both the temperature gradient and magnetic field. However, the values of the thermoelectric and thermomagnetic coefficients were found to be independent of the direction of the applied magnetic field with respect to the InSb sample surface.
5164 2015 YRen Two-Dimensional Field Effect TransistorsYi Ren
This document provides an introduction to two-dimensional field effect transistors (2D FETs). It first discusses the limitations of conventional FETs as their size is reduced according to Moore's Law. 2D FETs are proposed as a way to continue increasing transistor density by using atomically thin 2D materials as the channel layer. The document then discusses properties of graphene and transition metal dichalcogenides, which are common materials used in 2D FET channels. Finally, examples of 2D FETs using MoS2 and other materials as the channel layer are described.
Thermodynamics of magnetic refrigeration cycles are discussed. Key points:
1. Magnetic refrigeration uses the magnetocaloric effect where applying/removing a magnetic field causes materials to heat up/cool down.
2. Cyclic magnetic refrigeration processes are analyzed using thermodynamic potentials and the first law of thermodynamics. Formulas for work, heat, enthalpy and entropy are presented.
3. Common thermodynamic cycles for magnetic refrigeration like Brayton, Ericsson and Carnot cycles are examined. Cascade and regeneration principles can be applied to widen the achievable temperature range.
domain theory hysteresis loop and magnetioresistance.pptxKiruthikaKiruthi12
This document discusses domain theory of ferromagnetism and its applications in soft and hard magnetic materials. It explains that ferromagnetic materials are divided into small regions called domains, where magnetic moments are aligned in the same direction within each domain but vary between domains, resulting in zero net magnetization. When an external magnetic field is applied, the domains rotate or the domain walls move to align with the field. This causes hysteresis, as explained by the hysteresis loop. Soft magnetic materials have low coercivity and hysteresis losses, making them easily magnetized and demagnetized, while hard magnetic materials have high coercivity and retain magnetization, making them suitable for permanent magnets. Common soft magnetic materials include transformer steel and in
Electron Beam Machining (Modern ManufacturingProcess)Dinesh Panchal
The document summarizes electron beam machining (EBM). EBM uses a focused beam of high-energy electrons to melt and vaporize metal, allowing for precise machining. There are two types - thermal EBM uses the beam's heat to selectively vaporize material, while non-thermal EBM causes surface chemical reactions. The document discusses the generation and control of electron beams, the physical processes involved in thermal EBM, and a phenomenological theory of non-thermal EBM film growth proposed by Christly.
201606_Ferrites,_CMC,_and_Power_Transformer_(1)eRay Lai
The document discusses soft ferrite specifications for CMCs, power chokes, and transformers. It begins by explaining the importance but also limitations of the B-H curve as a characterization of ferrite materials. Key specifications discussed include permeability, saturation flux density, core loss density, and effective bandwidth. However, the document notes that permeability is nonlinear and dependent on factors like temperature, frequency, and load/current. Real applications also involve more complex geometries compared to an idealized toroid shape. Overall, both material properties from the B-H curve as well as mechanical design aspects are important for magnetic component design.
Toru Hara proposes developing an "ultimate energy storage device" with both high energy density like a battery and high power density like a supercapacitor. Specifically, Hara aims to develop a mono-atomic layer FeOOH/NiOOH battery using 3D interpenetrated electrode architectures deposited on graphene paper current collectors to enable efficient ion and electron transport for high performance. If successful, this battery could offer long cycle life by avoiding phase changes during charge/discharge that can destroy crystal structures in conventional battery materials.
Magnetostatic Surface Waves in a Left Handed / Ferrite/ Metal-Strip-Grating ...ijrap
The dispersion characteristics for magnetostatic surface waves in a left handed ( LHM)/ferrite/ metal-stripgrating structure have been investigated. We found that, the waveguide supports backward TE waves
since both permittivity and magnetic permeability of LHM are negative. We also illustrated the
dependence of wave frequency on the reduced wave number for a grating shielding parameter, g values
restricted by the range 0 ≤ g ≥ 1. It is shown that the grating shielding parameter, g induces
magnetostatic backward shorter waves . The leakage through the grating increases with the wave number.
The shorter backward magnetostatic waves are guided by the thicker waveguide where the best
confinement is achieved .
Similar to Permanent magnets: Plugging the gap (20)
The Free Energy Secrets of Cold ElectricityNOMADPOWER
The phenomenon of consumer devices becoming cold as they consume power is a sign that "Cold Electricity" is powering a consuming device. In terms of its form, "Cold Electricity" also has a voltage supply that produces the same current as a conventional power source. Conventional power from the grid generates work on consuming devices and at the same time gives off heat. But with a Cold Electricity supply, the power-consuming loads tend to absorb the temperature in the environment, meaning they do not emit heat but, on the contrary, collect heat, i.e., get cold during operation.
An Experimental Study on the Migration of Pb in the Groundwater Table Fluctua...NOMADPOWER
As a result of fluctuations in the shallow groundwater table, hydrodynamic conditions change alongside environmental conditions and hydrogeochemical processes to affect pollutant migration. The study aimed to investigate the migration, adsorption, and desorption characteristics of Pb on fine, medium, and coarse sand in the water table fluctuation zone by using several laboratory methods, including the kinetic aspects of Pb2+ adsorption/desorption and water table fluctuation experiments.
An optimized snowmelt lysimeter system for monitoring melt rates and collecti...NOMADPOWER
The contribution of snow meltwater to catchment streamflow can be quantified through hydrograph separation analyses for which stable water isotopes (18 O, 2 H) are used as environmental tracers. For this, the spatial and temporal variability of the isotopic composition of meltwater needs to be captured by the sampling method. This study compares an optimized snowmelt lysimeter system and an unheated precipitation collector with focus on their ability to capture snowmelt rates and the isotopic composition of snowmelt.
Adsorptive/photo-catalytic process for naphthalene removal from aqueous media...NOMADPOWER
The problem being addressed in this study is the removal of naphthalene from aqueous media using an adsorptive/photo-catalytic process. The proposed solution involves the use of an in-situ nickel doped titanium nanocomposite as a catalyst to degrade the naphthalene molecules. The effectiveness of this process is being tested in order to provide a potential solution for the removal of naphthalene from industrial wastewater and other contaminated water sources.
USE THE LASER ENGRAVING MACHINES TO ACHIEVE LASER CLEANING, LASER POST-MELTIN...NOMADPOWER
The document is an internship report summarizing Han Jin's three-month internship at Apex Europe B.V. in the Netherlands. It describes three projects conducted during the internship: 1) using laser engraving machines to clean inks from used anilox rolls without damaging the ceramic surface, 2) using laser post-melting of anilox rolls after engraving to replace finishing processes, and 3) investigating surface tension and roughness changes after laser treatment. The report provides details on the experiments conducted for each project, including testing different laser parameters and measurement of results. It also includes background context on flexographic printing and the role of anilox rolls in the printing process.
This document summarizes an experimental study of earth batteries as an alternative energy source. Various metal combinations were tested as electrodes, with zinc-copper cells providing around 0.9 volts. Small electronic devices were successfully powered by individual cells. Increasing the number of cells in series increased the voltage output linearly, while connecting cells in parallel increased the current output. Further testing aimed to optimize electrode materials and configurations to increase power levels for potential applications in remote areas lacking electricity access.
FIRST AID FOR SOLDIERS FM 21-11, Special Operations Forces Medical HandbookNOMADPOWER
These manuals meets the first aid training needs of individual service
members. Because medical personnel will not always be readily available,
the nonmedical service members must rely heavily on their own skills and
knowledge of life-sustaining methods to survive on the integrated battlefield.
This publication outlines both self-aid and aid to other service members
(buddy aid). More importantly, it emphasizes prompt and effective action in
sustaining life and preventing or minimizing further suffering and disability.
First aid is the emergency care given to the sick, injured, or wounded before
being treated by medical personnel. The term first aid can be defined as
“urgent and immediate lifesaving and other measures, which can be
performed for casualties by nonmedical personnel when medical personnel
are not immediately available.” Nonmedical service members have received
basic first aid training and should remain skilled in the correct procedures for
giving first aid. This manual is directed to all service members. The
procedures discussed apply to all types of casualties and the measures
described are for use by both male and female service members.
I should only close epidermal wounds, and then only if I must because I cannot get proper medical help to do it for me. (I know I will be soundly criticized for that comment, but I am entitled to my opinion, even if you disagree with it.)
Suturing should be low on my list of options for closing a wound. I should keep the book available as a reference for a trained medical professional. Deep wounds require special care, which means expertise beyond the training most of us non- professionals can acquire and maintain.
If I absolutely must close a wound that really needs a doctor to do it, I need this book to have a chance of doing a decent job of it.
Survival Personal Wilderness Medical KitNOMADPOWER
Most of us would agree that at any moment we could find ourselves in a disaster or other emergency situation. Even if this fact is only lurking in the back of the mind just below consciousness, the statement is no less true. Anyone can suddenly be thrust into an emergency situation or have a disaster land squarely upon them quite unexpectedly. How well one survives or IF one survives may be a matter of luck. Far better to invest some time and effort in survival preparedness.
Most will not met the harsh invironment that is talked about in thhe book. Most will never find themselves in need of knowing half of what is in the book. But everyone should have the book close at hand. With the rise of crime and terrorisem there are many good point that one can learn from not only this manual, but the others tha come with it. One could say we are in our time at the same point that Rome was just before its fall. Does that help you understand why you should get this "Handbook"? I would have given it a higher rating but we are talking about a military manual, not writen for bedtime reading.
Sustainable Strategies for the Exploitation of End-of-Life Permanent MagnetsNOMADPOWER
Rare Earth Magnets (REM), especially the NdFeB type, are essential components in high-performance electric motors and wind turbines, playing an important role in the shift towards a low-carbon energy matrix. However, little work has been done to understand how the production of REM can be in line with the global sustainable transition. To overcome this lack and help with future research, as well as decision-making, this paper provides a literature overview of which aspects of sustainability are being investigated in the REM supply chain, and how each of them contributes to achieving Sustainable Development Goals (SDG). This research is developed through a consistent analysis of 44 peer-reviewed publications, followed by an analysis of strengths, weaknesses, opportunities, and threats. Four main subjects of studies were identified: environmental impact; social impact; economic aspects and circular economy. Most of the studies focus on computing the environmental impact through life cycle assessment and discussing techniques towards exploring the circular economy concept. In addition to contributing to a greener economy, the majors identified strengths of REM are the great potential of its supply chain in reducing primary resource extraction, since REM recovery and recycling seem to be viable, and the promising techniques to minimize environmental impacts along the rare earth elements production chain.
In the focus of attention at the present time are the new rare earth‐cobalt‐based magnet alloys. This paper is primarily a qualitative review of the physical phenomena controlling their behavior and of the materials problems these magnets have posed. It also provides an outlook at possibilities for the development of still better or cheaper permanent magnets which current research on rare earth‐ transition metal alloys appears to provide. The origins of the magnetic moments and the crystal anisotropy of rare earth‐transition metal phases are discussed. Alternative concepts of the causes of coercivity in powders and sintered bodies are analyzed. Some basic aspects of the sintering of R‐Co compacts and the magnetic hardening of R–Co–Cu alloys in the massive state are reviewed. Specific problems related to particular alloys and applications of the magnets are pointed out. The conclusion is drawn that the new family of permanent magnets now emerging rivals in complexity both the Alnicos and the ferrites together. There are many development opportunities for the future, and we can expect that, eventually, magnets based on high‐anisotropy alloys containing rare earths will be offered in a variety of grades, covering a wide range of properties and prices, and that they will be produced by several drastically different methods.
Characteristics of Nd-Fe-B Permanent Magnets Present in Electronic ComponentsNOMADPOWER
In the present study the amount of permanent magnets (PM) present in waste of electrical and electronic equipment (WEEE) has been quantified. The PM was subsequently characterised by – among other techniques – scanning electron microscopy (SEM) using the TESCAN FEG-SEM MIRA3. The SEM results show that the magnets containing rare earth elements (REE) present in WEEE consist of Nd- Fe-B alloy in a tetrahedral form with an inter-granular space rich in REEs (Nd, Dy and Pr). About 20 μm thick coating layer consisting of Ni, Zn or an alloy of Cu/Ni is detected at the surface of the magnets. Properties of the PM at high temperatures are further investigated.
Climate Impact of Software Testing at Nordic Testing DaysKari Kakkonen
My slides at Nordic Testing Days 6.6.2024
Climate impact / sustainability of software testing discussed on the talk. ICT and testing must carry their part of global responsibility to help with the climat warming. We can minimize the carbon footprint but we can also have a carbon handprint, a positive impact on the climate. Quality characteristics can be added with sustainability, and then measured continuously. Test environments can be used less, and in smaller scale and on demand. Test techniques can be used in optimizing or minimizing number of tests. Test automation can be used to speed up testing.
UiPath Test Automation using UiPath Test Suite series, part 5DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 5. In this session, we will cover CI/CD with devops.
Topics covered:
CI/CD with in UiPath
End-to-end overview of CI/CD pipeline with Azure devops
Speaker:
Lyndsey Byblow, Test Suite Sales Engineer @ UiPath, Inc.
Full-RAG: A modern architecture for hyper-personalizationZilliz
Mike Del Balso, CEO & Co-Founder at Tecton, presents "Full RAG," a novel approach to AI recommendation systems, aiming to push beyond the limitations of traditional models through a deep integration of contextual insights and real-time data, leveraging the Retrieval-Augmented Generation architecture. This talk will outline Full RAG's potential to significantly enhance personalization, address engineering challenges such as data management and model training, and introduce data enrichment with reranking as a key solution. Attendees will gain crucial insights into the importance of hyperpersonalization in AI, the capabilities of Full RAG for advanced personalization, and strategies for managing complex data integrations for deploying cutting-edge AI solutions.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
UiPath Test Automation using UiPath Test Suite series, part 6DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 6. In this session, we will cover Test Automation with generative AI and Open AI.
UiPath Test Automation with generative AI and Open AI webinar offers an in-depth exploration of leveraging cutting-edge technologies for test automation within the UiPath platform. Attendees will delve into the integration of generative AI, a test automation solution, with Open AI advanced natural language processing capabilities.
Throughout the session, participants will discover how this synergy empowers testers to automate repetitive tasks, enhance testing accuracy, and expedite the software testing life cycle. Topics covered include the seamless integration process, practical use cases, and the benefits of harnessing AI-driven automation for UiPath testing initiatives. By attending this webinar, testers, and automation professionals can gain valuable insights into harnessing the power of AI to optimize their test automation workflows within the UiPath ecosystem, ultimately driving efficiency and quality in software development processes.
What will you get from this session?
1. Insights into integrating generative AI.
2. Understanding how this integration enhances test automation within the UiPath platform
3. Practical demonstrations
4. Exploration of real-world use cases illustrating the benefits of AI-driven test automation for UiPath
Topics covered:
What is generative AI
Test Automation with generative AI and Open AI.
UiPath integration with generative AI
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
AI 101: An Introduction to the Basics and Impact of Artificial IntelligenceIndexBug
Imagine a world where machines not only perform tasks but also learn, adapt, and make decisions. This is the promise of Artificial Intelligence (AI), a technology that's not just enhancing our lives but revolutionizing entire industries.
Dr. Sean Tan, Head of Data Science, Changi Airport Group
Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
Building Production Ready Search Pipelines with Spark and MilvusZilliz
Spark is the widely used ETL tool for processing, indexing and ingesting data to serving stack for search. Milvus is the production-ready open-source vector database. In this talk we will show how to use Spark to process unstructured data to extract vector representations, and push the vectors to Milvus vector database for search serving.
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Speck&Tech
ABSTRACT: A prima vista, un mattoncino Lego e la backdoor XZ potrebbero avere in comune il fatto di essere entrambi blocchi di costruzione, o dipendenze di progetti creativi e software. La realtà è che un mattoncino Lego e il caso della backdoor XZ hanno molto di più di tutto ciò in comune.
Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
BIO: Sostenitrice del software libero e dei formati standard e aperti. È stata un membro attivo dei progetti Fedora e openSUSE e ha co-fondato l'Associazione LibreItalia dove è stata coinvolta in diversi eventi, migrazioni e formazione relativi a LibreOffice. In precedenza ha lavorato a migrazioni e corsi di formazione su LibreOffice per diverse amministrazioni pubbliche e privati. Da gennaio 2020 lavora in SUSE come Software Release Engineer per Uyuni e SUSE Manager e quando non segue la sua passione per i computer e per Geeko coltiva la sua curiosità per l'astronomia (da cui deriva il suo nickname deneb_alpha).
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
We will explore the capabilities of AI in understanding XML markup languages and autonomously creating structured XML content. Additionally, we will examine the capacity of AI to enrich plain text with appropriate XML markup. Practical examples and methodological guidelines will be provided to elucidate how AI can be effectively prompted to interpret and generate accurate XML markup.
Further emphasis will be placed on the role of AI in developing XSLT, or schemas such as XSD and Schematron. We will address the techniques and strategies adopted to create prompts for generating code, explaining code, or refactoring the code, and the results achieved.
The discussion will extend to how AI can be used to transform XML content. In particular, the focus will be on the use of AI XPath extension functions in XSLT, Schematron, Schematron Quick Fixes, or for XML content refactoring.
The presentation aims to deliver a comprehensive overview of AI usage in XML development, providing attendees with the necessary knowledge to make informed decisions. Whether you’re at the early stages of adopting AI or considering integrating it in advanced XML development, this presentation will cover all levels of expertise.
By highlighting the potential advantages and challenges of integrating AI with XML development tools and languages, the presentation seeks to inspire thoughtful conversation around the future of XML development. We’ll not only delve into the technical aspects of AI-powered XML development but also discuss practical implications and possible future directions.
HCL Notes and Domino License Cost Reduction in the World of DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
Join HCL Ambassador Marc Thomas in this webinar with a special guest appearance from Franz Walder. It will give you the tools and know-how to stay on top of what is going on with Domino licensing. You will be able lower your cost through an optimized configuration and keep it low going forward.
These topics will be covered
- Reducing license cost by finding and fixing misconfigurations and superfluous accounts
- How do CCB and CCX licenses really work?
- Understanding the DLAU tool and how to best utilize it
- Tips for common problem areas, like team mailboxes, functional/test users, etc
- Practical examples and best practices to implement right away
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
Communications Mining Series - Zero to Hero - Session 1DianaGray10
This session provides introduction to UiPath Communication Mining, importance and platform overview. You will acquire a good understand of the phases in Communication Mining as we go over the platform with you. Topics covered:
• Communication Mining Overview
• Why is it important?
• How can it help today’s business and the benefits
• Phases in Communication Mining
• Demo on Platform overview
• Q/A
Best 20 SEO Techniques To Improve Website Visibility In SERPPixlogix Infotech
Boost your website's visibility with proven SEO techniques! Our latest blog dives into essential strategies to enhance your online presence, increase traffic, and rank higher on search engines. From keyword optimization to quality content creation, learn how to make your site stand out in the crowded digital landscape. Discover actionable tips and expert insights to elevate your SEO game.
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
1. Viewpoint Paper
Permanent magnets: Plugging the gap
J.M.D. Coey
School of Physics and CRANN, Trinity College, Dublin 2, Ireland
Available online 3 May 2012
Abstract—Bulk permanent magnets are indispensable components of numerous consumer and industrial products for energy con-
version. The market splits roughly 2:1 between Nd–Fe–B and hard ferrite, whose costs are currently in a ratio of more than 25:1.
The escalation of rare earth costs presents an opportunity for new magnets with an energy product of 100–200 kJ m3
, intermediate
between ferrite (38 kJ m3
) and Nd–Fe–B (200 kJ m3
), provided the costs of raw materials and manufacturing are kept low.
Ó 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Keywords: Hard magnets; Coercivity; Rare-earth alloys; Oxides
1. Introduction
Permanent magnets have evolved in the last 60 years
from classroom curiosities, with a handful of specialized
applications in small motors, dynamos and microwave
generators to indispensable components of many mass-
market consumer goods, medical devices and industrial
products. The majority of these are some sort of electro-
magnetic energy converter—motors, actuators or gener-
ators. Magnet ownership by an average middle-class
family has shot up a hundred-fold, from one or two
magnets to one or two hundred, although most people
would be hard pressed is asked to say where their mag-
nets are to be found. If we count the individually
addressable patches of magnetization on computer hard
discs, which are becoming increasingly indistinguishable
from permanent magnets, then magnet ownership rock-
ets by a further nine orders of magnitude!
The magnet revolution has been brought about by
the development of new hard magnetic materials. By a
“hard magnet” we mean one with a broad hysteresis
loop, which is a plot of the magnetization M of the
material vs. the magnetic field H acting on it. The loop
is nonlinear, and it depends on time, temperature and
the prior history of the magnet [1]. The breakthrough
that occurred in the early 1950s in the Netherlands [2]
was the shattering of the “shape barrier”. Before that,
mass-market magnets had to be manufactured in awk-
ward shapes in order to avoid self-demagnetization.
The bars and horseshoes of yesteryear were needed to
reduce the negative contribution to H from the demag-
netizing field Hd produced by the magnet itself. This
field is approximately related to the magnetization by
the simple expression:
Hd N M; ð1Þ
where N is a number between 0 and 1 that depends only
on the magnet shape. Hence the field acting is
H = H0 + Hd where H0 is the externally applied field.
A magnetic material which exhibits an M(H) hysteresis
loop that has the form of a square or a squat rectangle
can be made in any desired shape without demagnetiz-
ing itself. We can properly speak of the form of the loop
when both M and H are measured in the same units of
kA m1
.
The ideal hysteresis loop for a permanent magnet is
illustrated in Figure 1. A true permanent magnet can
be fabricated in any desired shape, which means that
coercivity must exceed the saturation magnetization:
Hc Ms: ð2Þ
This does not imply that magnets should made in
shapes which minimize Hd. On the contrary, such a
magnet would be just as useless as one which maximizes
it, because neither produces any stray field [3]. Stray
field is the raison d’être of a permanent magnet. The
job of the magnet is to produce a magnetic field outside
its volume, which we denote by the same symbol Hd
used for the field it produces within its volume. It is
the stray field which is channeled in a magnetic circuit
to provide the forces, torques, electromotive forces or
voltages on which magnet applications depend [1,3].
1359-6462/$ - see front matter Ó 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.scriptamat.2012.04.036
E-mail: jcoey@tcd.ie
Available online at www.sciencedirect.com
Scripta Materialia 67 (2012) 524–529
www.elsevier.com/locate/scriptamat
1. Electricity and Ether 2. Magnetic Generator 3. Top Magnetic Generator 4. Low RPM
2. The fundamental magnetic field is really B, not H
(although it is the value of H and its history that deter-
mine the state of a piece of magnetic material). In free
space the relation between the two is trivial:
B ¼ l0H; ð3Þ
where l0 is the magnetic constant, also known as the
permeability of free space, which is defined to be pre-
cisely 4p 107
T mA1
. B is therefore measured in tes-
las. Bold type has just been introduced to indicate that B
and H are vectors which only have to be parallel to each
other free space. Within a magnetic material, the rela-
tion becomes:
B ¼ l0ðH þ MÞ: ð4Þ
The B-field, also known as the magnetic flux density,
obeys Maxwell’s equation:
r:B ¼ 0; ð5Þ
which states that the B-field is divergenceless. It has no
sources or sinks, because free magnetic poles are never
observed in nature. The “north” and “south” poles, or
the equivalent positive and negative magnetic charge,
are fictitious. Nevertheless, they are useful to envisage
the H-field and magnetostatic calculations may be sim-
plified by invoking them as a computational aide [3].
The B(H) loop shown in Figure 1b corresponds to the
M(H) loop shown in Figure 1a.
It can be shown that the energy stored in the stray
field created by a magnet is equal to 1=2
R
jBHjdV ,
where the integral is over the magnet volume [3]. Assum-
ing that H and M are uniform, Eqs. (1) and (4) give:
jBHj ¼ l0M2
s ðN N
2
Þ: ð6Þ
Differentiating with respect to N to find the maxi-
mum, we obtain N ¼ 1=2, and jBHjMAX ¼ 1=4l0M2
s . A
shape which corresponds to N ¼ 1=2 is a low cylinder
of height roughly equal to its radius. Modern magnets
are often this shape.
If the magnetization curve deviates from the ideal
square loop of Figure 1a, the value of the maximum
achievable energy product |BH|max is lower than this, so:
jBHjmax 1=4l0M2
s : ð7Þ
For most applications, the figure of merit which we
seek to maximize in a magnetic material is |BH|max.
Nowadays, two families of magnets are produced on a
large scale. One is the ferrite family [4], which was devel-
oped in the Netherlands 60 years ago [3]. The common
phases are BaFe12O19 and SrFe12O19, which have the
hexagonal magnetoplumbite structure. The energy prod-
uct of these magnets does not exceed 38 kJ m3
, but they
are cheap and relatively easy to produce. Prices are less
than $5 kg1
. Ferrites represent about one-third of the
permanent magnet market, and the lion’s share by mass
of the million tonnes of magnets shipped each year.
Most of the remaining two-thirds are rare-earth per-
manent magnets, especially those based on Nd2Fe14B,
an iron-rich tetragonal phase that was independently
discovered in Japan [5] and in the USA [6] in 1982.
The best laboratory Nd–Fe–B magnets have energy
products as high as 470 kJ m3
, close to the theoretical
maximum of |BH|MAX = 512 kJ m3
. Commercial
grades with values as high as 400 kJ m3
are shipped.
Production in 2010 amounted to 80,000 tonnes, but
due to escalating rare-earth prices, Nd–Fe–B magnets
now cost more than $100 kg1
. There is growing de-
mand for superior grades with improved performance
at elevated temperatures for energy-related applications
such as electric vehicles and direct-drive wind turbines
[7]. Adequate hysteresis is maintained at temperatures
up to 200 °C by replacing some of the Nd by a heavy
rare earth, Dy or Tb. Unfortunately, the supply situa-
tion for heavy rare earths is particularly precarious;
the price of Dy or Tb is currently 10 times that of Nd,
whose price is currently running at 10 times its historical
level. The 3–10 wt.% of these elements in the formula is
now the major component of the price of high-tempera-
ture grades of Nd–Fe–B.
About 5% of the rare-earth magnets produced belong
to the Sm–Co family, which has been developed since
the mid-1960s [8,9]. These magnets have a similar field
of application to Dy-substituted Nd–Fe–B, offering im-
proved temperature stability, but lower energy product.
There remains a small but steady demand for the old
Alnico magnets [10]. An estimate of the breakdown of
magnet production in terms of market value in 2010 is
shown in Figure 2.
Processed magnets are frequently fully dense sintered,
oriented blocks produced by power metallurgy or cera-
mic methods. An alignment step to orient the easy axes
of all the crystallites is highly beneficial as without it the
remanent magnetization is decreased by more than a
factor of 2, and the energy product by a factor of 4
(Eq. (7)). However, there are benefits in loading the
magnet powder in a polymer matrix, to make mouldable
Nd -Fe -B
Sm -Co
Alnico
Ferrite
Figure 2. Estimated breakdown of the world market for permanent
magnets in 2010. The total value is approximately $9 bn (after Ref. [7]).
H
M
H
B
Hc B
Hc
Ms Br
(a) (b)
Figure 1. Ideal hysteresis loops for a permanent magnet: (a) an M(H)
loop and (b) a B(H) loop. The maximum possible energy product
|BH|MAX is represented by the area of the largest square that can be
drawn in the second quadrant.
J. M. D. Coey / Scripta Materialia 67 (2012) 524–529 525
1. Electricity and Ether 2. Magnetic Generator 3. Top Magnetic Generator 4. Low RPM
3. or flexible magnets. The packing fraction of the mag-
netic material may reach 70%, so the magnetization is
reduced in this proportion, and the energy product is re-
duced by a factor of 2. Figure 3 illustrates the range of
energy products for the main classes of magnets pro-
duced today.
The escalating costs of rare earths is a manifestation
of the “rare earth crisis” [11]. It is forcing attention to be
paid to the possibilities of substitution, cost reduction
and recycling. Broadly, three approaches are under
investigation:
Reduce the heavy rare-earth content of Nd–Fe–B-
type magnets, while preserving their high-tempera-
ture performance. The heavy rare earths Dy or Tb
are required if the coercivity is to remain stable with
increasing temperature up to 200 °C.
Seek a novel ultra-high-performance material to
replace rare-earth magnets.
Seek a new, low-cost material with a maximum
energy product lying in the gap between ferrite and
rare-earth magnets.
Considerable progress is being made with the first ap-
proach. By optimized processing and grain boundary
engineering it should be reduce the heavy rare-earth
content by about a factor of three from its present levels
of upto 10 wt.% [12].
The second approach is problematic. Nd2Fe14B is a
close-to-ideal high-performance magnet [13]. It is largely
made of iron, the cheap and abundant ferromagnetic
element with the greatest magnetization. The anisotropy
K = 4.9 MJ m3
is mostly provided by the relatively
inexpensive light rare earth Nd (which has an abun-
dance similar to that of zinc), which couples with its mo-
ment parallel to that of iron, and only a small amount of
a third element, boron, is required to stabilize a uniaxial
structure, which has an easy axis of magnetization. All
obvious candidates, including exchange spring nano-
composites, have been considered, and quite a lot of re-
search has been done on them [14]. The difficulty is that
an energy product in excess of 500 kJ m3
requires
Ms 1.3 MA m1
. The coercivity should be as large as
this for a square loop, but an upper limit for the coerciv-
ity is set by the anisotropy field Ha = 2K1/l0Ms, where
K1 is the uniaxial anisotropy constant. Past experience
with new permanent magnet materials indicates that
years of optimization are usually needed to achieve a
coercivity that is even a quarter of the anisotropy field,
because permanent magnetism and hysteresis are meta-
stable phenomena that depend on subtle details of the
microstructure which can only be optimized by pains-
taking experimentation [15]. An empirical criterion for
a permanent magnet is that the hardness parameter j
should be greater than unity [1,3]:
j ¼ ðK=l0M2
s Þ
1=2
1: ð8Þ
This implies that K l0M2
s 2 MJ m3
. Such large
values of K demand magnetocrystalline anisotropy,
which arises from spin–orbit coupling. The maximum
anisotropy that can be achieved by controlling the shape
of nanoscale magnetized regions, the approach adopted
for Alnico [10], is only a quarter as large. Strong spin–
orbit coupling requires the presence of a heavy element
such as a member of the 4d, 4f or 5d series [3]. These are
costly elements, as may be seen from the periodic table
in Figure 4. Nd–Fe–B is really hard to beat.
Strictly speaking, the absolute minimum condition
for a true permanent magnet is Ha Hc Ms, which re-
duces to j 1=
ffiffiffi
2
p
. The maximum energy product could
even be obtained for a magnet with N ¼ 1=2 provided
Hc Ms/2 (j 1/2). However, all existing materials
have j 1 (SrFe12O19, 1.33; SmCo5, 4.3; Sm2Co17,
1.89; Nd2Fe14B, 1.54). A breakthrough in magnet pro-
cessing that would relax the condition (8) is conceivable,
but on past experience it seems highly unlikely.
In this Viewpoint article we will therefore accept the
condition (8) and explore the third approach. Can we
hope to find a new, cheap material that is significantly
better than ferrite?
2. New magnets with moderate performance
The prospect is to fill the gap between ferrite and
rare-earth magnets with something cheap and effective.
Such a material could enhance the performance and re-
duce the weight of devices that currently use ferrite, and
greatly cut the cost of devices that currently use rare-
earth magnets, at the expense of some increase in
weight.
A point worth emphasizing is that our quest is to
make M, the magnetic moment per unit volume, as large
as possible, while satisfying the condition (8), K l0M2
s ,
without the use of expensive elements. Furthermore the
material needs to be thermally stable and posses a Curie
temperature in excess of 550 K if it is to have a realistic
prospect of being adopted for practical purposes.
A modern approach to the problem of finding such a
material would be to begin with combinatorial computa-
tional materials science to screen thousands of alloys, and
identify perhaps a dozen candidate materials which sat-
isfy the constraints of Curie temperature, magnetization,
anisotropy and cost, and then proceed to try to make
them in the laboratory. However, little use seems to have
been made of this approach so far. It should be tried.
Instead we will discuss a few plausible candidate
materials, analyse why they fall short, and see what
might be done about it. In Table 1, we set out the basic
1 5 10 50 100 500
Coerci
vity (kA
m-1
)
Energy Product (kJ m-1
)
10
100
1000
10000 A B C
Figure 3. Ranges of energy product and coercivity for different types
of permanent magnets. Colour code is the same as in Figure 2. Bonded
magnets are shown stippled. (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of
this article.)
526 J. M. D. Coey / Scripta Materialia 67 (2012) 524–529
1. Electricity and Ether 2. Magnetic Generator 3. Top Magnetic Generator 4. Low RPM
4. requirements for new materials with three levels of en-
ergy product.
It should be emphasized that these are minimum
requirements. In particular, we should not forget that
the |BH|max achieved with real hysteresis loops always
falls short of the ideal |BH|MAX for a square loop.
Table 2 summarizes the properties of a few interesting
uniaxial ferromagnetic compounds. It is possible to
achieve any individual target value, but no material
quite manages to combine the required TC, Ms, K and
energy product.
The magnetization of all the materials in Table 2
meets the minimum target value of Ms, except for
Mn2Ga, which has a ferrimagnetic structure [17]. Man-
ganese is an abundant element which forms alloys which
may exhibit high Curie temperatures. Atomic moments
can be higher than those of either iron or cobalt. The
difficulty is that the Mn atoms on high-moment sites
tend to couple antiferromagnetically. Ferromagnetic
coupling occurs for long bond lengths, as in tetragonal
MnAl, but there half the volume is occupied by non-
magnetic Al; the magnetization in this and other equi-
atomic compounds is necessarily small [3], although it
may suffice for target A in Table 1. A nonmagnetic con-
stituent will normally reduce the magnetization of an al-
loy since it occupies volume without contributing to the
magnetic moment. Interstitial elements (B, C, N) may be
exceptions. Hexagonal MnBi is another interesting
material, but although the materials cost per kg looks
affordable, bismuth is a scarce element obtained as a
byproduct of lead, with an annual production of only
8000 tonnes. It makes little sense to try to develop MnBi
as a mass-market permanent magnet, because the bis-
muth cost would then rise to prohibitive levels. The
same argument can be made for gallium in Mn2Ga, or
any related composition with Ga or Ge.
One lesson to be taken from Table 2 is that the rare
earths are not indispensable for strong uniaxial anisot-
ropy. Provided the axial distortion of the structure is
sufficient, useful uniaxial anisotropy may be found for
Mn, Fe or Co. Mn2Ga, which has the tetragonal D022
structure, which may be regarded as a severely distorted
C1b half-Heusler structure, and YCo5, which has the
hexagonal D2d stucture, are cases in point. Both have
K 2 MJ m3
. The contribution of the 3d sublattice in
magnets such as SmCo5 and Nd2Fe14B to the overall
uniaxial anistropy can be seen from the data on the yt-
trium analogues in Table 2. The presence of a heavy
nonmagnetic atom may help to enhance the spin–orbit
coupling at the 3d site by hybridization, but examples
in the Table 2 show that it is by no means essential.
However, the anisotropy needed to make a magnet
permanent rises quadratically with the magnetization
(Eq. (8)). For a00
Fe16N2, an interstitial compound that
is only stable at low temperature and is very difficult to
prepare in bulk in single-phase form [18], but which has
a magnetization approaching 2 MA m1
, Eq. (8) requires
K 5 MJ m3
. Unfortunately this is 5 times the mea-
sured value. Interstitial D011 Fe3C also has j much too
small to make a true permanent magnet. Co3C may be
a bit better [19].
The tetragonal L10 structure is potentially interesting,
but if only half the atoms in the alternating c-plane lay-
ers are magnetic, as in sMnAl, the magnetization is inev-
itably limited. Tetragonal MnAl is a permanent magnet
material but |BH|MAX is only 112 kJ m3
. Developments
that have taken place stabilizing the s phase with carbon
have produced material with |BH|max of up to 50 kJ m3
Figure 4. The cost periodic table (November 2011), including information on the magnetic properties of the elements.
Table 1. Some target specifications for new magnet materials.
|BH|MAX
kJ m3
TC K Ms MA m1
K kJ m3
Raw materials
cost $ kg1
A 100 550 570 500 10
B 150 550 690 750 20
C 200 550 800 1000 30
J. M. D. Coey / Scripta Materialia 67 (2012) 524–529 527
1. Electricity and Ether 2. Magnetic Generator 3. Top Magnetic Generator 4. Low RPM
5. [20]. MnAl magnets are machinable and light. The L10
alloys CoPt and FePt are suitable for permanent mag-
nets. In fact PtCo was discovered in 1936 (by Jelling-
haus), and it was probably the first true permanent
magnet. The values of Ms and j are 0.80 MA m1
and
2.47 for CoPt and 1.14 MA m1
and 2.02 for FePt,
respectively. Energy products of up to 100 kJ m3
are
reported for these materials [16], but the materials cost
is prohibitive for any mass-market application.
A feature of L10 materials is that they undergo a
tetragonal to face-centred cubic (fcc) phase transition
at an elevated temperature Tt. The permanent magne-
tism obviously disappears in the cubic phase, and the
maximum operating temperature has to be one where
there is no tendency for atomic disordering in the sites
of the tetragonal structure. A particularly interesting
example of an L10 compound is sFeNi. It is found in
iron meteorites which have had billions of years to reach
thermal equilibrium. The value of Tt is only 320 °C [21].
The phase been prepared by neutron irradiation of fcc
FeNi [22]. The value of K is 0.32 MJ m3
, and j 0.4.
Included in Table 2 are compounds with the Nd2Fe14B-
or SmCo5-type structures having the nonmagnetic Y atom
in place of the rare earth. Replacement of the magnetic rare
earth by some mixture of the cheaper nonmagnetic ele-
ments Y, La or Ce could offer significant cost savings. Co-
balt, which costs approximately $30 kg1
, is a constraint
on the application of D2d structure MCo5 materials.
It is worth emphasizing that the relative amounts of
the different rare earths obtained from a mine depends
on the relative proportion of the metals in the ore, which
in turn reflects the local crystal abundances. The Sm:Nd
ratio is typically about 1:5, so Sm may be now regarded
as a byproduct of Nd production, and in the absence of
balanced demand it may fetch a lower price than Nd.
This is the case at present (late 2011). Since the produc-
tion of Sm–Co magnets is currently about 5% of that of
Nd–Fe–B (Fig. 2), it may be economically viable to use
Sm–Co instead of Nd–Fe–B, despite the relatively costly
Co. Sm–Co magnets are traditionally more expensive
than Nd–Fe–B, because of higher raw materials and
manufacturing costs. However, the price of Sm is cur-
rently lower than that of Nd, and 17 times less than that
of Dy, an element with similar crustal abundance. At the
moment, the raw materials costs for Nd–Fe–B with 9%
Dy are $340 kg1
, compared with $75 kg1
for a 2:17
Sm–Co magnet. This illustrates the importance of
matching demand to the relative distribution of the
rare-earth elements in the ores that are being mined, in
order to make the best use of nature’s gifts.
Another example where the price is unrelated to the
abundance is the Dy/Tb pair. Although the abundance
of Tb is five times less than that of Dy it sells for almost
the same price because it serves a similar purpose—to
increase the anisotropy constant of Nd–Fe–B magnets
and thereby improve their high-temperature perfor-
mance. It has no other significant use, except for small
amounts required for phosphors. The current rare-earth
crisis is largely a problem of heavy rare earth supply.
There are abundant ores containing the light rare earths
Pr, Nd and Sm in various parts of the world, but known
reserves of the heavy rare earths Dy and Tb outside Chi-
na are very limited in relation to possible demand over
the next ten years.
The examples considered in Table 2 are all interme-
tallic or interstitial metallic compounds. One might ask
whether there is any prospect of finding an oxide perma-
nent magnet with better properties than hexagonal fer-
rite. Part of the reason for the low magnetization of
SrFe12O19 (Ms = 0.38 MA m1
) is the fact that much
of the volume is occupied by large O2
anions, which
carry no magnetic moment. Another problem, however,
is that the oxide is ferrimagnetic rather than ferromag-
netic. If the moments of the Fe3+
sublattices were all
aligned, the magnetization would be 3 times as great
and energy products of 300 kJ m3
could be envisioned.
How could we ensure that the 3d moments in an oxide
couple parallel, with a high Curie temperature? Ferro-
magnetic oxides are not unknown; CrO2 is the textbook
example, with a 2/3 full t2g band for Cr4+
[3]. Most other
oxide ferromagnets, such as the perovskite manganites,
rely on mixed valence to provide ferromagnetic dou-
ble-exchange coupling. Further efforts might throw up
a uniaxial, ferromagnetic mixed-valence oxide with a
high TC, but it seems unlikely as oxides have already
been intensively investigated [23].
Finally, it is worth remarking that the specifications
of materials used for perpendicular magnetic recording
with bit-patterned media and perpendicular magnetic
random-access memory are increasingly coming to res-
semble those for permanent magnets. The stability con-
dition for 10-year data retention:
D ¼ KV =kT 60 ð9Þ
demands K 0.5 MJ m3
in media where the free layer
volume or bit volume is 500 nm3
(10 nm 10 nm
5 nm). Thin-film materials CoPt, FePt have been consid-
ered for this purpose, but thin films of Pt-free materials
with less expensive elements such as MnGa2 can be envis-
aged [24]. For perpendicular media, the anisotropy field
2K/l0Ms must overcome the demagnetizing field
Hd Ms, so that K 1=2l0M2
s . In the case of Mn2Ga,
this condition reads K 0.14 MJ m3
, which is comfort-
ably satisfied. The bits could even be a factor of 2 smal-
ler. Unlike bulk applications, one can consider using a
much wider range of materials in Table 2 for thin films
because cost is no longer such a severe contraint. The
quantities of materials used in a thin-film memory are
Table 2. Properties of some uniaxial ferromagnets [3,16,17].
MnAl MnBi Mn2Ga Y2Fe14B a00
Fe16N2 Fe3C YCo5
Ms (MA m1
) 0.60 0.58 0.47 1.10 1.92 1.09 0.85
K1 (MJ m3
) 1.7 0.90 2.35 1.1 1.0 0.45 6.5
TC (K) 650 628 770 590 810 56 987
j 1.95 1.46 2.35 0.85 0.43 0.55 2.7
Raw materials cost ($ kg1
) 10 20 100 30 10 10 50
528 J. M. D. Coey / Scripta Materialia 67 (2012) 524–529
1. Electricity and Ether 2. Magnetic Generator 3. Top Magnetic Generator 4. Low RPM
6. tiny, perhaps of the order of 1 lg, 7 orders of magnitude
less than in a bulk energy conversion device. Neverthe-
less, if either Pt- or Pd-based alloys were to be widely
adopted for magnetic media or memory, there would
be a strain on the global market for scarce platinum
group metals. A cubic meter would provide 5 billion peo-
ple with a 20 cm2
of a film 10 nm thick, but this would
represent half the world’s annual production of Pt.
3. Conclusions
Despite everything that has already been done on the
topic, it is possible to be optimistic about the prospects
of developing a relatively cheap magnet that could hit
targets A–C in Table 1 and Figure 3. In sMnAl we al-
ready have a material which, given an effort comparable
to that which has been devoted to optimizing Nd2Fe14B
where |BH|max/|BH|MAX is now 0.93, should be able to
meet target A. Whether or not the process will be cost
effective remains to be seen.
The pressure to come up with some new magnets that
has been generated by the rare-earth crisis looks set to
continue in the medium term. Ultimately the supply sit-
uation for the light rare earths is expected to ease as new
mines are opened [25], and new reserves such as those on
the sea-bed are exploited [26]. The heavy rare earths Dy
and Tb are more problematic, so long as demand relative
to Nd outweighs their relative abundance in available
ores [25]. The current elevated and unstable prices of
these elements is likely to act as a disincentive to develop-
ing new, high-volume applications of Nd–Fe–B magnets
such as direct-drive wind turbines and electric vehicles.
Computation methods of combinational materials
science may be the key to further progress. We need to
see if some cheap new ternary or quaternary phases
can be found. Binaries have been exhaustively explored,
and the possibilities there are well known.
As scientists looking for new perpendicular media
and those seeking new low-cost permanent magnets
are converging onto some sort of common ground, it
can be expected that in the future one community will
increasingly learn from the other.
Acknowledgements
This work was supported by Science Foundation Ire-
land as part of the NISE project, contract number 10/
IN1.I3006.
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