This document summarizes research on using electric fields to control the magnetic states of FeGa nanomagnets. Key findings include:
1) An electric field was used to rotate the magnetization of some isolated FeGa nanomagnets by up to 400 degrees. The new magnetization state persisted after removing the electric field, demonstrating a non-volatile effect.
2) In dipole-coupled nanomagnet pairs with one "hard" and one "soft" nanomagnet, an electric field rotated the soft nanomagnet's magnetization by over 900 degrees due to influence from the hard nanomagnet.
3) Being able to control nanomagnet states with
Investigation of Anomalous Thrust and Proposal for Future ExperimentationBrian Kraft
The document summarizes an experiment investigating anomalous thrust from an asymmetric resonant cavity. A second phase is proposed using a copper frustum cavity excited in the TE011 mode by a 200W solid state amplifier at 1.8-2.4GHz. Computer simulations will ensure resonance. The apparatus will use a pendulum to measure thrust to a resolution of 0.5mN. Previous experiments observed anomalous thrust but results varied due to inconsistent procedures. The second phase aims to replicate previous experiments more rigorously.
Analysis of Simple Maglev System using SimulinkArslan Guzel
The document is a PowerPoint presentation analyzing a simple maglev system using Simulink. It includes:
- An introduction to maglev systems and their applications.
- Circuit diagrams and explanations of the position sensor, electromagnet actuator, and other system components.
- Derivations of the system's mathematical model and equations in state space form for both nonlinear and linear controller approaches.
- Descriptions of the Simulink models created to simulate the system, including blocks for the generalized system, nonlinear controller, and determining voltage and current.
- Analysis of simulation results for two air gap scenarios, comparing graphs of position, velocity, acceleration, and other signals between the scenarios.
Investigation of Anomalous Thrust from a Partially Loaded Resonant CavityBrian Kraft
Three key points:
1) Over four months, tests were conducted to test the EM Drive propulsion concept using a partially loaded resonant cavity. A thrust measurement apparatus was built with 0.5 mN accuracy.
2) Finite element simulations informed the design of a cylindrical cavity partially loaded with dielectrics. Resonances were found using a Vector Network Analyzer. Displacements observed corresponded to 2.4 mN of thrust but perpendicular displacements of unknown cause were also observed.
3) Further funding is needed to refine the experimental apparatus and reduce uncertainties in order to fully validate or refute the EM Drive concept.
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.
When a superconducting material is placed in a uniform magnetic field below its critical temperature (Tc) and critical field (Hc), the magnetic field lines are expelled from the material. This is known as the Meissner effect. Key properties of superconductors include zero electrical resistance below Tc, loss of superconductivity above Hc or a critical current density (Jc). Type I superconductors transition directly from superconducting to normal states above these thresholds, while Type II have an intermediate mixed state between lower and upper critical fields (Bc1 and Bc2). Applications of superconductors include generation of strong magnetic fields, particle accelerators, MRI machines, power transmission, and quantum computing.
Abstract: In this paper circuit for coilgun is simulated and analyzed using SIMULINK. Behavior of the magnetic field due to the current carrying coil is analyzed. Also, the effect on the coilgun performance for different weights of projectiles is investigated. The speed profile for different positions of the projectile is observed which is a critical parameter for coilgun operation. A comparison is drawn between the simulated and experimental results.
Great pyramid giza alternative energy pg circular timestavennerpride
1) The authors have found that the dimensions of the Great Pyramid of Giza express key ratios related to sine waves and Fibonacci numbers. They hypothesize that the pyramid shape could function as a wideband antenna for capturing atmospheric electrostatic discharge (ESD) impulses.
2) Experiments show that a pyramid-shaped transducer can absorb ESD impulses from an electrostatic field and convert them into exponentially decaying sinusoidal waveforms.
3) Through an inductive coil system, the transducer is able to transfer power from the captured ESD impulses. Measurements indicate the system can achieve efficiencies of around 20-30% in transferring power.
Investigation of Anomalous Thrust and Proposal for Future ExperimentationBrian Kraft
The document summarizes an experiment investigating anomalous thrust from an asymmetric resonant cavity. A second phase is proposed using a copper frustum cavity excited in the TE011 mode by a 200W solid state amplifier at 1.8-2.4GHz. Computer simulations will ensure resonance. The apparatus will use a pendulum to measure thrust to a resolution of 0.5mN. Previous experiments observed anomalous thrust but results varied due to inconsistent procedures. The second phase aims to replicate previous experiments more rigorously.
Analysis of Simple Maglev System using SimulinkArslan Guzel
The document is a PowerPoint presentation analyzing a simple maglev system using Simulink. It includes:
- An introduction to maglev systems and their applications.
- Circuit diagrams and explanations of the position sensor, electromagnet actuator, and other system components.
- Derivations of the system's mathematical model and equations in state space form for both nonlinear and linear controller approaches.
- Descriptions of the Simulink models created to simulate the system, including blocks for the generalized system, nonlinear controller, and determining voltage and current.
- Analysis of simulation results for two air gap scenarios, comparing graphs of position, velocity, acceleration, and other signals between the scenarios.
Investigation of Anomalous Thrust from a Partially Loaded Resonant CavityBrian Kraft
Three key points:
1) Over four months, tests were conducted to test the EM Drive propulsion concept using a partially loaded resonant cavity. A thrust measurement apparatus was built with 0.5 mN accuracy.
2) Finite element simulations informed the design of a cylindrical cavity partially loaded with dielectrics. Resonances were found using a Vector Network Analyzer. Displacements observed corresponded to 2.4 mN of thrust but perpendicular displacements of unknown cause were also observed.
3) Further funding is needed to refine the experimental apparatus and reduce uncertainties in order to fully validate or refute the EM Drive concept.
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.
When a superconducting material is placed in a uniform magnetic field below its critical temperature (Tc) and critical field (Hc), the magnetic field lines are expelled from the material. This is known as the Meissner effect. Key properties of superconductors include zero electrical resistance below Tc, loss of superconductivity above Hc or a critical current density (Jc). Type I superconductors transition directly from superconducting to normal states above these thresholds, while Type II have an intermediate mixed state between lower and upper critical fields (Bc1 and Bc2). Applications of superconductors include generation of strong magnetic fields, particle accelerators, MRI machines, power transmission, and quantum computing.
Abstract: In this paper circuit for coilgun is simulated and analyzed using SIMULINK. Behavior of the magnetic field due to the current carrying coil is analyzed. Also, the effect on the coilgun performance for different weights of projectiles is investigated. The speed profile for different positions of the projectile is observed which is a critical parameter for coilgun operation. A comparison is drawn between the simulated and experimental results.
Great pyramid giza alternative energy pg circular timestavennerpride
1) The authors have found that the dimensions of the Great Pyramid of Giza express key ratios related to sine waves and Fibonacci numbers. They hypothesize that the pyramid shape could function as a wideband antenna for capturing atmospheric electrostatic discharge (ESD) impulses.
2) Experiments show that a pyramid-shaped transducer can absorb ESD impulses from an electrostatic field and convert them into exponentially decaying sinusoidal waveforms.
3) Through an inductive coil system, the transducer is able to transfer power from the captured ESD impulses. Measurements indicate the system can achieve efficiencies of around 20-30% in transferring power.
1) Electromechanical energy conversion theory represents electromagnetic force or torque in terms of device variables like currents and mechanical displacement.
2) An electromechanical system consists of an electric system, mechanical system, and means for them to interact via a coupling field.
3) The total energy supplied to the coupling field equals the energy transferred from the electric system plus the energy transferred from the mechanical system.
Radioactivity -- The Absorption of Gamma Rays by MatterRyan Dudschus
This paper shows my finding of how the energy of gamma rays that are emitted from a source are effected when lead sheets, with a range of thickness, are placed between the source and the Geiger-Mueller tube.
This paper shows my ability to figure out several unknown circuit configurations with the use of an oscilloscope and an AC power supply. the properties of diodes were also investigated.
Isolation of MIMO Antenna with Electromagnetic Band Gap StructureAysu COSKUN
This work represents isolation of mimo antenna system with mushroom type electromagnetic band gap structure in order to reduce mutual coupling between antennas.
This document provides definitions and explanations of key concepts in SPM Physics 2009, including:
1) Definitions of speed, velocity, momentum, Newton's laws of motion, balanced and unbalanced forces, work, and energy.
2) Explanations of pressure, Pascal's principle, Archimedes' principle, and Bernoulli's principle.
3) Descriptions of wave reflection, refraction, diffraction, interference, and sound waves.
4) Overviews of circuits, electromagnetism, induced current, and direct/alternating current.
5) Definitions of nucleon number, isotopes, radioactivity, nuclear fission, and nuclear fusion.
Eric dollard introduction to dielectric and magnetic discharges in electrical...PublicLeaker
This document contains two parts. Part I is a chapter from a book on dielectric and magnetic discharges in electrical windings. It discusses capacitance and how energy can be stored both magnetically through inductance and electrically through dielectric fields. Part II is a 1919 paper on electrical oscillations in antennae and induction coils by J.M. Miller.
IONIC POLARIZATION ANDDIELECTRIC RESONANCE..Polarization is the separation of positive and negative charges in a system so that there is a net electric dipole moment per unit volume.
Ionic polarization is polarization caused by relative displacements between positive and negative ions in ionic crystals.
This type of polarization occurs in ionic crystals such as NaCl, KCl etcs.
Dielectric resonance occurs when the frequency of the applied ac field is such that there is maximum energy transfer from the ac voltage source to heat in the dielectric through the alternating polarization and depolarization of the molecules by the ac field.
This document discusses different methods for treating the star point of generators, including isolated, compensated, indirectly earthed via reactor/transformer/resistor, and directly earthed. It focuses on earthing the star point via a neutral earthing resistor as the most practical method. It describes the components, wiring, and protections involved in this method, including requirements to ensure only one generator is earthed at a time. Dimensioning considerations for the resistor to limit earth fault current are also covered.
Dielectric properties can be measured using an impedance analyzer. A dielectric is a material with a permanent electric dipole moment. Dipoles have equal and opposite charges separated by a small distance. The dielectric constant is the ratio of a material's permeability to the permeability of free space. When an electric field is applied to a dielectric, the electric charges are displaced and dipoles are induced, causing polarization. An impedance analyzer can measure properties like impedance, resistance, susceptance, and dielectric constant of materials over a range of frequencies. It provides information on the performance of components like capacitors, inductors, and resistors. Dielectrics used in applications must have properties like high resistivity, strength, fire resistance and low losses
This document provides an introduction to wireless power transfer via strongly coupled magnetic resonances, also known as WiTricity. It discusses the history of wireless power transfer ideas from Nikola Tesla's experiments to recent developments by MIT professors in 2006. The key concept of WiTricity is that it overcomes limitations of previous wireless power methods by using strongly coupled magnetic resonances to improve efficiency and transfer power over greater distances than magnetic induction alone. Technical details are then provided on magnetic induction, inductive coupling, and resonance to explain how WiTricity works.
An electromagnetic field is produced by moving electrically charged objects and affects other charged objects near it. It is one of the fundamental forces of nature and results from a combination of electric and magnetic fields. Electromagnetism underlies many daily phenomena and is governed by four main laws. Electric fields arise from voltage while magnetic fields arise from current flow. Electromagnets have many uses including in electric bells, sorting scrap metal, and speakers. Transformers change voltage levels in power transmission lines to reduce energy losses. Exposure to electromagnetic fields is increasing due to modern technology but typically does not pose health risks.
This document describes a design for a piezoelectric shock absorber that can generate electricity from vehicle vibrations. It discusses two initial designs - electromagnetic and hydraulic - and proposes using a piezoelectric crystal installed within the shock absorber. When compressed, the crystal generates electric energy from the force. The design aims to limit the force on the crystal for safety while still producing optimal voltage. Analysis shows the design could generate over 25V from manual impacts. The piezoelectric shock absorber could increase fuel efficiency in hybrids or power accessories in other vehicles.
Eric dollard introduction to dielectric and magnetic discharges in electrical...PublicLeaker
This document summarizes a book chapter about capacitance and inductance. It discusses:
1) How capacitance represents electrical energy storage in a field between two conductors.
2) Common misconceptions about capacitance and how lines of force can better represent dielectric fields.
3) How inductance is analogous to capacitance, with energy stored in a magnetic field as loops of force around a conductor.
4) The limits of zero resistance (trapping energy in a field) and infinite resistance (instantly releasing energy), which can produce powerful effects in the latter case.
This document discusses synchronous motors and provides information on:
- The key differences between synchronous motors and induction motors, including excitation type, speed, starting capability, and efficiency.
- The advantages of synchronous motors such as ability to operate at lagging or leading power factor and disadvantages like higher cost and need for external excitation.
- The equivalent circuit model of a cylindrical rotor synchronous motor and voltage equation.
- The operation of a synchronous motor at no load and under loaded conditions, explaining how an increase in load causes the rotor to lag the stator by the load angle to draw more current.
- Phasor diagrams showing the voltage and current relationships under lagging and leading power factor operation.
- An example numerical
This document discusses semiconductor materials and their properties. It covers elemental and compound semiconductors, including gallium nitride used in LEDs. It describes the band structure of semiconductors including the valence and conduction bands separated by the bandgap. Carrier generation and recombination processes are explained. Intrinsic and extrinsic semiconductors are defined based on their carrier concentrations.
This lecture provides an overview of electromagnetic fields and Maxwell's equations. It introduces key concepts including electric and magnetic fields, Maxwell's equations in integral and differential form, electromagnetic boundary conditions, and electromagnetic fields in materials. Maxwell's equations are the fundamental laws of classical electromagnetics and govern all electromagnetic phenomena. The lecture also discusses phasor representation for time-harmonic fields.
The document discusses pulsed electromagnetic field (PEMF) therapy. It explains that PEMF therapy uses electromagnetic coils to generate magnetic fields above 100 Gauss, which can provide therapeutic effects on tissues. The document outlines several medical conditions that PEMF therapy may help, such as arthritis, fractures, and wound healing. It also provides examples of how PEMF therapy increased blood flow and accelerated healing in cases of fractures and osteoarthritis based on before and after thermography images.
- Early experiments in magnetism date back to ancient Greeks and Chinese who observed magnetic properties.
- In the 13th century, Pierre de Maricourt discovered magnetic field lines and the existence of magnetic poles.
- In the 1820s, experiments by Faraday, Henry and others established the connection between electricity and magnetism.
- A magnetic field is generated by moving electric charges or magnetic materials. It exerts a force on moving charges perpendicular to both the field and velocity vectors.
- The motion of a charged particle in a magnetic field follows a circular or helical path depending on its orientation to the field.
- Magnetic fields are produced by magnets and by moving electric charges like electric currents. A magnetic field has both a magnitude and direction at each point in space and can exert forces on moving charges.
- The magnetic force on a moving charged particle depends on the charge and current, magnetic field strength and direction, and the particle's velocity. Right hand rules can be used to determine the direction of the magnetic force.
- Charged particles moving in a magnetic field experience a force perpendicular to both their velocity and the magnetic field, causing them to travel in a circular path. The magnetic force does no work on charged particles.
1. The document reports on reversible strain-induced magnetization switching between two stable/metastable states in ~300 nm sized FeGa nanomagnets placed on a piezoelectric PMN-PT substrate. Applying a voltage of one polarity generates compressive strain and switches the magnetization to one state, while a voltage of the opposite polarity generates tensile strain and switches it back to the original state.
2. This allows the two states to encode binary bits ('0' and '1'), and either bit can be written deterministically by choosing the correct voltage polarity, providing an ultra-low energy "non-toggle" memory.
3. The experiment demonstrates this reversible switching between two distinct magnet
This document discusses magnetic levitation and summarizes:
1. Magnetic levitation works by using magnetic fields to repel magnetic materials and lift or propel objects without touching.
2. It relies on principles of ferromagnetism, diamagnetism, and eddy currents induced in conductors by changing magnetic fields.
3. Magnetic levitation shows potential for fast, smooth mass transit but faces challenges with stability, power requirements, and cooling superconductors.
1) Electromechanical energy conversion theory represents electromagnetic force or torque in terms of device variables like currents and mechanical displacement.
2) An electromechanical system consists of an electric system, mechanical system, and means for them to interact via a coupling field.
3) The total energy supplied to the coupling field equals the energy transferred from the electric system plus the energy transferred from the mechanical system.
Radioactivity -- The Absorption of Gamma Rays by MatterRyan Dudschus
This paper shows my finding of how the energy of gamma rays that are emitted from a source are effected when lead sheets, with a range of thickness, are placed between the source and the Geiger-Mueller tube.
This paper shows my ability to figure out several unknown circuit configurations with the use of an oscilloscope and an AC power supply. the properties of diodes were also investigated.
Isolation of MIMO Antenna with Electromagnetic Band Gap StructureAysu COSKUN
This work represents isolation of mimo antenna system with mushroom type electromagnetic band gap structure in order to reduce mutual coupling between antennas.
This document provides definitions and explanations of key concepts in SPM Physics 2009, including:
1) Definitions of speed, velocity, momentum, Newton's laws of motion, balanced and unbalanced forces, work, and energy.
2) Explanations of pressure, Pascal's principle, Archimedes' principle, and Bernoulli's principle.
3) Descriptions of wave reflection, refraction, diffraction, interference, and sound waves.
4) Overviews of circuits, electromagnetism, induced current, and direct/alternating current.
5) Definitions of nucleon number, isotopes, radioactivity, nuclear fission, and nuclear fusion.
Eric dollard introduction to dielectric and magnetic discharges in electrical...PublicLeaker
This document contains two parts. Part I is a chapter from a book on dielectric and magnetic discharges in electrical windings. It discusses capacitance and how energy can be stored both magnetically through inductance and electrically through dielectric fields. Part II is a 1919 paper on electrical oscillations in antennae and induction coils by J.M. Miller.
IONIC POLARIZATION ANDDIELECTRIC RESONANCE..Polarization is the separation of positive and negative charges in a system so that there is a net electric dipole moment per unit volume.
Ionic polarization is polarization caused by relative displacements between positive and negative ions in ionic crystals.
This type of polarization occurs in ionic crystals such as NaCl, KCl etcs.
Dielectric resonance occurs when the frequency of the applied ac field is such that there is maximum energy transfer from the ac voltage source to heat in the dielectric through the alternating polarization and depolarization of the molecules by the ac field.
This document discusses different methods for treating the star point of generators, including isolated, compensated, indirectly earthed via reactor/transformer/resistor, and directly earthed. It focuses on earthing the star point via a neutral earthing resistor as the most practical method. It describes the components, wiring, and protections involved in this method, including requirements to ensure only one generator is earthed at a time. Dimensioning considerations for the resistor to limit earth fault current are also covered.
Dielectric properties can be measured using an impedance analyzer. A dielectric is a material with a permanent electric dipole moment. Dipoles have equal and opposite charges separated by a small distance. The dielectric constant is the ratio of a material's permeability to the permeability of free space. When an electric field is applied to a dielectric, the electric charges are displaced and dipoles are induced, causing polarization. An impedance analyzer can measure properties like impedance, resistance, susceptance, and dielectric constant of materials over a range of frequencies. It provides information on the performance of components like capacitors, inductors, and resistors. Dielectrics used in applications must have properties like high resistivity, strength, fire resistance and low losses
This document provides an introduction to wireless power transfer via strongly coupled magnetic resonances, also known as WiTricity. It discusses the history of wireless power transfer ideas from Nikola Tesla's experiments to recent developments by MIT professors in 2006. The key concept of WiTricity is that it overcomes limitations of previous wireless power methods by using strongly coupled magnetic resonances to improve efficiency and transfer power over greater distances than magnetic induction alone. Technical details are then provided on magnetic induction, inductive coupling, and resonance to explain how WiTricity works.
An electromagnetic field is produced by moving electrically charged objects and affects other charged objects near it. It is one of the fundamental forces of nature and results from a combination of electric and magnetic fields. Electromagnetism underlies many daily phenomena and is governed by four main laws. Electric fields arise from voltage while magnetic fields arise from current flow. Electromagnets have many uses including in electric bells, sorting scrap metal, and speakers. Transformers change voltage levels in power transmission lines to reduce energy losses. Exposure to electromagnetic fields is increasing due to modern technology but typically does not pose health risks.
This document describes a design for a piezoelectric shock absorber that can generate electricity from vehicle vibrations. It discusses two initial designs - electromagnetic and hydraulic - and proposes using a piezoelectric crystal installed within the shock absorber. When compressed, the crystal generates electric energy from the force. The design aims to limit the force on the crystal for safety while still producing optimal voltage. Analysis shows the design could generate over 25V from manual impacts. The piezoelectric shock absorber could increase fuel efficiency in hybrids or power accessories in other vehicles.
Eric dollard introduction to dielectric and magnetic discharges in electrical...PublicLeaker
This document summarizes a book chapter about capacitance and inductance. It discusses:
1) How capacitance represents electrical energy storage in a field between two conductors.
2) Common misconceptions about capacitance and how lines of force can better represent dielectric fields.
3) How inductance is analogous to capacitance, with energy stored in a magnetic field as loops of force around a conductor.
4) The limits of zero resistance (trapping energy in a field) and infinite resistance (instantly releasing energy), which can produce powerful effects in the latter case.
This document discusses synchronous motors and provides information on:
- The key differences between synchronous motors and induction motors, including excitation type, speed, starting capability, and efficiency.
- The advantages of synchronous motors such as ability to operate at lagging or leading power factor and disadvantages like higher cost and need for external excitation.
- The equivalent circuit model of a cylindrical rotor synchronous motor and voltage equation.
- The operation of a synchronous motor at no load and under loaded conditions, explaining how an increase in load causes the rotor to lag the stator by the load angle to draw more current.
- Phasor diagrams showing the voltage and current relationships under lagging and leading power factor operation.
- An example numerical
This document discusses semiconductor materials and their properties. It covers elemental and compound semiconductors, including gallium nitride used in LEDs. It describes the band structure of semiconductors including the valence and conduction bands separated by the bandgap. Carrier generation and recombination processes are explained. Intrinsic and extrinsic semiconductors are defined based on their carrier concentrations.
This lecture provides an overview of electromagnetic fields and Maxwell's equations. It introduces key concepts including electric and magnetic fields, Maxwell's equations in integral and differential form, electromagnetic boundary conditions, and electromagnetic fields in materials. Maxwell's equations are the fundamental laws of classical electromagnetics and govern all electromagnetic phenomena. The lecture also discusses phasor representation for time-harmonic fields.
The document discusses pulsed electromagnetic field (PEMF) therapy. It explains that PEMF therapy uses electromagnetic coils to generate magnetic fields above 100 Gauss, which can provide therapeutic effects on tissues. The document outlines several medical conditions that PEMF therapy may help, such as arthritis, fractures, and wound healing. It also provides examples of how PEMF therapy increased blood flow and accelerated healing in cases of fractures and osteoarthritis based on before and after thermography images.
- Early experiments in magnetism date back to ancient Greeks and Chinese who observed magnetic properties.
- In the 13th century, Pierre de Maricourt discovered magnetic field lines and the existence of magnetic poles.
- In the 1820s, experiments by Faraday, Henry and others established the connection between electricity and magnetism.
- A magnetic field is generated by moving electric charges or magnetic materials. It exerts a force on moving charges perpendicular to both the field and velocity vectors.
- The motion of a charged particle in a magnetic field follows a circular or helical path depending on its orientation to the field.
- Magnetic fields are produced by magnets and by moving electric charges like electric currents. A magnetic field has both a magnitude and direction at each point in space and can exert forces on moving charges.
- The magnetic force on a moving charged particle depends on the charge and current, magnetic field strength and direction, and the particle's velocity. Right hand rules can be used to determine the direction of the magnetic force.
- Charged particles moving in a magnetic field experience a force perpendicular to both their velocity and the magnetic field, causing them to travel in a circular path. The magnetic force does no work on charged particles.
1. The document reports on reversible strain-induced magnetization switching between two stable/metastable states in ~300 nm sized FeGa nanomagnets placed on a piezoelectric PMN-PT substrate. Applying a voltage of one polarity generates compressive strain and switches the magnetization to one state, while a voltage of the opposite polarity generates tensile strain and switches it back to the original state.
2. This allows the two states to encode binary bits ('0' and '1'), and either bit can be written deterministically by choosing the correct voltage polarity, providing an ultra-low energy "non-toggle" memory.
3. The experiment demonstrates this reversible switching between two distinct magnet
This document discusses magnetic levitation and summarizes:
1. Magnetic levitation works by using magnetic fields to repel magnetic materials and lift or propel objects without touching.
2. It relies on principles of ferromagnetism, diamagnetism, and eddy currents induced in conductors by changing magnetic fields.
3. Magnetic levitation shows potential for fast, smooth mass transit but faces challenges with stability, power requirements, and cooling superconductors.
This document provides an overview of magnetic circuits and induction in electrical machines. It begins by outlining the learning outcomes, which are to understand the principles behind electromagnets and their relationship to voltage and magnetic materials. It then defines electric machines as devices that convert between electrical and mechanical power. The rest of the document discusses key concepts related to magnetism and induction that are important for understanding electric machines, including electromagnets, magnetic fields, flux, flux linkage, Faraday's law, Lenz's law, and induced voltages. Worked examples are provided to illustrate how to apply these concepts.
This document provides an introduction to giant magnetoresistance (GMR), including its discovery in the late 1980s and commercial applications in hard disk drives. GMR is observed in thin film structures with alternating ferromagnetic and nonmagnetic layers, where resistance decreases significantly (typically 10-80%) in the presence of a magnetic field. The effect is explained using a model where resistance is lower when magnetic moments of ferromagnetic layers are parallel versus antiparallel. The document describes different types of structures that exhibit GMR, including magnetic multilayers, spin valves, pseudo-spin valves, and granular thin films.
This document provides an overview of magnetism and magnetic fields. It begins with an introductory activity on magnetism facts. The document then outlines topics to be covered, including magnetic fields, forces on moving charges and currents, and properties of electromagnets and ferromagnets. Examples are provided to demonstrate how to calculate magnetic field strength and forces. The key points are that magnets produce magnetic fields with north and south poles; magnetic fields exert forces on moving charges; and currents generate magnetic fields according to Ampere's law.
Giant magnetoresistance and their applicationsPremashis Kumar
Giant magnetoresistance (GMR) is a quantum mechanical magnetoresistance effect observed in multilayers composed of alternating ferromagnetic and non-magnetic conductive layers. The 2007 Nobel Prize in Physics was awarded to Albert Fert and Peter Grünberg for the discovery of GMR.
The effect is observed as a significant change in the electrical resistance depending on whether the magnetization of adjacent ferromagnetic layers are in a parallel or an antiparallel alignment. The overall resistance is relatively low for parallel alignment and relatively high for antiparallel alignment. The magnetization direction can be controlled, for example, by applying an external magnetic field. The effect is based on the dependence of electron scattering on the spin orientation.
FERROMAGNETIC-FERROELECTRIC COMPOSITE 1D NANOSTRUCTURE IN THE PURSUIT OF MAGN...ijrap
Nanocomposites of linear chain of ferroelectric-ferromagnetic crystal structure is considered. It is analyzed
theoretically in the motion equation method on the pursuit of magnonic excitations,lattice vibration
excitations and their interactions leading to a new collective mode of excitations,the electormagnons. In
this particular work, it is observed that the magnetizations and polarizations are tunable in a given temperature ranges for some specific values of the coupling order parameter.
Ferromagnetic-Ferroelectric Composite 1D Nanostructure in the Pursuit of Magn...ijrap
The document summarizes a theoretical analysis of a 1D nanocomposite structure consisting of linear chains of ferroelectric and ferromagnetic crystals. The analysis considers:
1) Magnetic and lattice vibration excitation modes are derived from Hamiltonians describing magnetic interactions and lattice oscillations.
2) An interaction Hamiltonian describes how magnetic and lattice excitations couple via strain mediation.
3) The effective Hamiltonian is used to derive an expression for the excitation frequency of new "electromagnons" arising from hybridized magnetic and lattice excitations.
4) Expressions for how the magnetization of the structure varies with temperature based on the excitation energy are presented.
This document discusses magnetizing current and its effect on synchronous motors. [1] Magnetizing current orients magnetic domains to store energy in the form of a magnetic field. [2] The current lags voltage by 90 degrees in ideal cases but lags less in actual cases due to hysteresis. [3] Synchronous motors require magnetizing current from the AC source to maintain a constant air gap flux for constant terminal voltage.
Magnetic materials form magnetic domains to minimize their magnetostatic energy. Domain walls separate domains with different magnetization orientations. Bloch walls have spins rotating continuously across the wall, while Neel walls have spins rotating in the plane of the wall. The equilibrium domain size and wall thickness are determined by a balance of exchange, anisotropy, magnetostatic, and wall energies. Various techniques like SEMPA, MFM, and magneto-optical imaging are used to observe domain structures with high resolution.
Novel Design of a Magnetically Switchable MOSFET using Magnetoresistive ElementsTELKOMNIKA JOURNAL
Various research activities have been carried out, individually, in the fields of MOSFET design andanalysis, and magnetoresistance; however, ourresearch focused on the design and analysis of a magnetically switchable MOSFET with the application of magnetoresistive elements. Theoretical study, calculations and simulations were used in order to design and analyze the magnetically switchable MOSFET. It was observed that the magnetoresistance values of 42%, 81% and 95%, respectively, for giant magnetoresistive element, tunneling magnetoresistive element and colossal magnetoresistive element resulted in reduced resistance values of 139.2Ω, 45.6Ω and 12Ω across the MOSFET in presence of magnetic field; as compared to a higher value of 240Ω in its absence. As a consequence, the gate-source voltage increased beyond the threshold value (1.5V), and the MOSFET switched ON. Accordingly, a magnetically switchable MOSFET was designed and its behavioural characteristics were analyzed.
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.
Geprags strain controlled magnetic science_direct_2014Phạm Công
1) The document investigates approaches to achieve nonvolatile switching of magnetization in ferromagnetic thin films using strain from piezoelectric actuators.
2) Experiments on Fe3O4 thin film/piezoelectric hybrids show significant strain-induced changes in magnetization, but domain formation limits switching.
3) A theoretical model demonstrates that with optimized engineering, strain could enable nonvolatile switching between two remanent magnetization states.
This chapter discusses magnetism and magnetic fields. It describes how magnets have north and south poles that attract or repel each other, and how electric currents produce surrounding magnetic fields. The chapter also defines the tesla as the unit of magnetic fields and explores how magnetic fields exert forces on both electric currents and moving electric charges.
The document discusses electromagnetic fields (EMF). It begins by defining EMF as a physical field produced by moving electrically charged objects that affects behavior of nearby charged objects. It notes EMF extends indefinitely through space and is one of four fundamental forces. The field combines electric fields from stationary charges and magnetic fields from moving charges. The document then provides examples of uses for electromagnets and discusses electromagnetic induction, transformers, exposure to EMF, and contrasts EMF with gravitational fields.
This document summarizes key topics related to magnetic effects of electric current, including:
1) A force is exerted on a current-carrying conductor placed in a magnetic field according to Fleming's Left Hand Rule. The direction of force can be determined by pointing fingers to show the direction of magnetic field, current, and resulting force.
2) An electric motor works by converting electrical energy to mechanical energy using a coil that rotates when placed in a magnetic field and current is passed through it.
3) Electromagnetic induction causes a current to be induced in a coil either by moving a magnet within the coil or changing the magnetic field near the coil. Michael Faraday discovered that relative motion between a magnet and coil produces
ppt magnetic field X class Module 2.pptNAAMMAcademy
This document summarizes key topics related to magnetic effects of electric current, including:
1) A force is exerted on a current-carrying conductor placed in a magnetic field according to Fleming's Left Hand Rule. The direction of force can be determined by pointing fingers to show the direction of magnetic field, current, and resulting force.
2) An electric motor works by converting electrical energy to mechanical energy using a coil that rotates when placed in a magnetic field and current is passed through it.
3) Electromagnetic induction causes a current to be induced in a coil either by moving a magnet near the coil or changing the magnetic field near the coil, as discovered by Michael Faraday.
In our conventional electronic devices we use semi conducting materials for logical operation and magnetic materials for storage, but spintronics uses magnetic materials for both purposes. These spintronic devices are more versatile and faster than the present one. One such device is Spin Valve Transistors (SVT).
Spin valve transistor is different from conventional transistor. In this for conduction we use spin polarization of electrons. Only electrons with correct spin polarization can travel successfully through the device. These transistors are used in data storage, signal processing, automation and robotics with less power consumption and results in less heat. This also finds its application in Quantum computing, in which we use Qubits instead of bits.
This document describes simple classroom demonstrations of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) principles. The demonstrations use common compasses to represent magnetic nuclei such as hydrogen-1 and carbon-13 placed in a static magnetic field generated by three aligned permanent magnets. An oscillating magnetic field from a stir plate or electromagnet pulse is used to excite the "nuclei". This causes the compass needles to precess, demonstrating the resonance condition. The demonstrations illustrate how NMR frequency depends on magnetic field strength and environmental factors. They provide an intuitive way for students to learn basic NMR and MRI concepts.
1. Electric field control of magnetic states in isolated and dipole-coupled
FeGa nanomagnets delineated on a PMN-PT substrate
Hasnain Ahmad1
, Jayasimha Atulasimha2
and Supriyo Bandyopadhyay3
1
Department of Electrical and Computer Engineering
2
Department of Mechanical and Nuclear Engineering
Virginia Commonwealth University, Richmond, VA 23284, USA
Corresponding author email: sbandy@vcu.edu
ABSTRACT
We report observation of a “non-volatile” converse magneto-electric effect in elliptical FeGa
nanomagnets delineated on a piezoelectric PMN-PT substrate. The nanomagnets are initially
magnetized with a magnetic field directed along their nominal major axis and subsequent
application of an electric field across the substrate generates strain in the substrate, which is
partially transferred to the nanomagnets and rotates the magnetizations of some of them to
metastable orientations. There they remain after the field is removed, resulting in “non-volatility”.
In isolated nanomagnets, the angular separation between the initial and final magnetization
directions is < 900
, but in a dipole-coupled pair consisting of one “hard” and one “soft”
nanomagnet, the soft nanomagnet's magnetization is rotated by > 900
from the initial orientation
because of the dipole influence of the hard nanomagnet. These effects can be utilized for ultra-
energy-efficient logic and memory devices.
The ability to control the magnetization states of nanomagnets with an electric field is alluring
fornanomagnetic logic and memory applications [1-8]. It also enables controlling nanoscale
magnetic fields with an electric field, which is a technological advance in its own right [9, 10].
Electric field control of magnetization in thin film heterostructures of ferromagnetic/ferroelectric
layers (artificial multiferroics) has been reported in the past by many groups [11-14]. This was
later extended to microscale artifical multiferroics [15, 16] and then to nanoscale artificial
multiferroics [17-19]. The latter [17-19] are of particular interest since, there, an electric field
generates strain in a pieozelectric layer which is transferred to a (magnetostrictive) ferromagnetic
layer in elastic contact with the piezoelectric layer, and this affects the ferromagnetic layer's
magnetization. Obviously, this can have device applications in rewritable non-volatile memory if
the ferromagnet persists in the new state and does not revert back to the old state after the electric
field is withdrawn. Ref. [17] reported evolving the magnetization state of a nanoscale
ferromagnet from a single domain state to a transitional domain state with an electric field. The
ferromagnet, however, reverted to its original single domain state after the electric field was
removed, making the effect “volatile'”. This volatility was also a feature of ref. [18]. Here, we
report a similar nanoscale converse magneto-electric effect in FeGa nanomagnets, but in our
case, the state that the magnetization is driven to by the electric field is metastable.
Consequently, when the electric field is withdrawn, the magnetization persists in the new state
2. and does not spontaneously return to the original state, resulting in “non-volatility”. Ref. [19]
also reported a similar non-volatile transition, but there the final state of magnetization was
stable instead of metastable. From the point of view of binary logic and memory applications, it
makes no difference whether the final state is stable or metastable as long as the metastable state
is robust against thermal perturbations (that is the case here since the nanomagnets driven to the
metastable state persist in that state indefinitely at room temperature). However, driving the
system from one stable state to a metastable state can be preferable to driving it to another stable
state if the energy barrier separating the first stable state and the metastable state is lower than
the energy barrier separating two stable states. In that case, the energy dissipated in the transition
will be lower, making it more attractive for device applications.
There is one other feature that distinguishes our work from past work. All previous work on
(electrically-generated) strain-induced nanomagnet switching [17-19] utilized elemental
magnetostrictive nanomagnets made of Co or Ni. They have relatively small saturation
magnetostriction and therefore would require relatively large electric fields to alter the
magnetization state. The alloy FeGa, on the other hand, has much higher magnetostriction [20,
21] and is therefore more desirable, but it also presents unique material challenges owing to the
existence of many phases [22, 23]. Nonetheless, there is a need to step beyond elemental
ferromagnets and examine compound or alloyed ferromagnets with much higher
magnetostriction to advance this field. There has been some work in FeGa thin films [24-27], but
not in nanoscale FeGa magnets which are important for nanomagnetic logic and memory
applications. This motivates our work.
Our system consists of elliptical FeGa nanomagnets of 200 - 350 nm feature size fabricated on a
(100)-oriented PMN-PT substrate (70% PMN and 30% PT). The fabrication involved electron
beam lithography and sputtering [see the accompanying supplementary material for details of
fabrication and material characterization]. The major axes of the elliptical nanomagnets are
aligned nominally parallel to each other on the substrate. Prior to delineation of the nanomagnets,
the PMN-PT substrate is poled with an electric field of 9 kV/cm in a direction that will coincide
with the major axes of the nanomagnets.
Fig. 1 shows atomic force (AFM) and magnetic force (MFM) micrographs of two nearly
elliptical isolated nanomagnets that are placed far enough away from each other to make dipole
interaction between them negligible. The nanomagnet nominal dimensions are: major axis = 335
nm, minor axis = 286 nm and thickness = 15 nm. Underneath each nanomagnet there is a ~5 nm
layer of Ti needed to adhere the nanomagnets to the PMN-PT substrate. This layer is thin enough
to allow most of the strain generated in the PMN-PT substrate (upon the application of an
electric field) to transfer to the FeGa nanomagnets resting on top. There is no capping layer on
the nanomagnets to prevent oxidation of FeGa since we found that to be a non-issue.
3. Figure 1: (a) Magnetic force (MFM) and atomic force (AFM) micrographs of isolated elliptical
nanomagnets that have been subjected to a strong magnetic field in the direction indicated by the vertical
green arrow. The resulting magnetization direction of the right nanomagnet is indicated by the slanted red
arrow. (b) The MFM image of the nanomagnets after they have been stressed with an electric field and
relaxed [stress withdrawn]. The magnetization direction of the left nanomagnet does not show any
discernible change, but the right nanomagnet's magnetization has rotated to a new orientation shown by
the slanted solid yellow arrow. For comparison, the initial orientation of this nanomagnet's magnetization
is shown by the broken red arrow. The magnetization has rotated by ~400
owing to the stress generated by
the electric field and subsequent removal of the electric field has not returned the magnetization to the
original state, but left it in the new state. (c) The poling direction and direction of electric field applied to
generate compressive stress along the nominal major axes of the nanomagnets.
The nanomagnets are initially magnetized in one direction along their major axes with a 1.5
Tesla magnetic field as shown by the vertical green arrow in Fig. 1(a). The MFM image in Fig.
1(a) shows that after the magnetizing field has been removed, the nanomagnets have close to a
single-domain state with their magnetizations pointing not quite along that of the applied
magnetic field, but reasonably close to it. The deviation could be due to lithography
imperfections [see the AFM images for the magnet topography] that make the shapes of the
nanomagnets slightly non-elliptical (which is why the stable orientation is not exactly along the
major axis) or the presence of pinning that pins the magnetization in an orientation subtending a
small angle with the major axis.
4. An electric field of 4.2 kV/cm is then applied across the PMN-PT substrate in the direction
opposite to the poling directionto generate compressive stress along the nanomagnets' major axes
(see Fig. 1(c)). This field is generated by applying a voltage of 2.1 kV across a 5 mm long
substrate and this voltage is within the linear strain-versus-voltage regime determined in ref.
[19]. This field strains the PMN-PT substrate owing to d33 coupling. The value of d33 measured
in our substrates in ref. [19] was 1000 pm/V. Therefore, the average strain generated in the
PMN-PT substrate is 420 ppm. If all of it is transferred to the FeGa nanomagnets, then the stress
generated in them is ~42 MPa since the Young's modulus of FeGa is about 100 GPa.
The nanomagnets are compressed in the direction of their major axes by the electric field and
since FeGa has a positive magnetostriction, this should rotate the magnetization of the
magnetized nanomagnets toward the minor axis because stress anisotropy relocates the potential
energy minimum to an orientation that is perpendicular to the stress axis. It is expected that after
the electric field (or stress) is removed, the magnetization will return to the original orientation,
or perhaps to some other orientation, since the potential energy landscape changes when stress is
withdrawn.
What we see, however, in the MFM image of Fig. 1(b) [post-stress condition] is that the left
nanomagnet's magnetization is indeed in the original orientation but the right nanomagnet's
magnetization is not. The left's magnetization is in the original orientation because it either did
not rotate at all [perhaps owing to the fact that the stress generated in it was insufficient to
overcome the shape anisotropy energy barrier in this nanomagnet and make its magnetization
rotate, or the magnetization was pinned by defects] or it did rotate but returned to the original
orientation after the removal of stress, as expected. What is interesting is that the right
nanomagnet's magnetization has assumed an orientation subtending an angle of ~400
with the
original. Clearly, in this nanomagnet, stress was able to overcome the shape anisotropy energy
barrier and budge the magnetization from its original orientation, but after stress withdrawal, the
magnetization settled into a different orientation and stayed there. This is obviously a metastable
orientation corresponding to a local potential minimum that is robust against thermal noise and
could have arisen either because the shape of the right nanomaget deviates significantly from
elliptical causing local minima to appear in the potential profile of the nanomagnet, or pinning
sites pin the magnetization in a given state after stress withdrawal, or there are multiple phases
that lead to multiple coercivities [28] associated with the presence of multiple energy barriers in
the potential profile separated by local energy minima. The stress anisotropy gives rise to an
effective magnetic field given by ( ) ( )03 2 /eff s sH Mλ s µ= , where sλ is the magnetostriction
coefficient, s is the stress, 0µ is the permeability of free space and Ms is the saturation
magnetization of the nanomagnet. If the material has two different coercivities H1 and H2 and the
inequality 1 2effH H H< < holds, then stress can get the magnetization stuck in a metastable
state. In the accompanying supplementary material, we show the magnetization curves of the
5. nanomagnets and they do seem to indicate the presence of multiple phases with different
coercivities. Therefore, this scenario is very likely.
There can be another feature peculiar to FeGa alloys. A recent paper suggests that there is
significant non-Joulian magnetostriction in FeGa alloys [29] which can complicate the stress-
induced magnetization rotation process in this materialand perhaps drive the magnetization to
metastable states.
No matter what the underlying mechanism is, in this case, the magnetization state of the right
nanomagnet has been altered with an electric field resulting in evolution of the magnetization
from one orientation to another. Equally important, this transformation is “non-volatile” because
the magnetization does not return to the original state after removal of the electric field.
Figure 2: (a) Same as Fig. 1(a), except there are four nanomagnets in this image. The initial magnetization
direction of the nanomagnet in the upper right corner is indicated by the slanted red arrow. (b) MFM
image after application and removal of stress. The magnetizations of all nanomagnets expect the one in
the upper right corner show no discernible difference between the pre- and post-stress conditions, but the
magnetization of the one in the upper right corner has rotated by ~820
. Notice that this nanomagnet is
most “circular” of all and therefore has the lowest shape anisotropy energy barrier, which is why stress
was able to rotate its magnetization.
6. To ascertain that this effect is repeatable, we examined another set of nanomagnets of slightly
different dimensions [major axis = 337 nm, minor axis = 280 nm and thickness = 16 nm]. The
corresponding AFM and MFM pictures are shown in Fig. 2. The three nanomagnets (among the
four shown) that have the highest shape anisotropy (highest eccentricity of the ellipse) do not
show any perceptible difference between the pre- and post-stress magnetization states [either
because their magnetizations did not rotate when stressed or returned to the original states after
stress removal], but the least shape anisotropic nanomagnet has evolved to a different state after
stress removal. The new state's magnetization has an angular separation of ~820
from the original
magnetization state. Once again, the new state is non-volatile. Altering the magnetization state of
a magnet with an electric field is the converse magnetoelectric effect. Therefore, we have
observed clear evidence of the converse magnetoelectric effect in the nanoscale and the effect
has the property of non-volatility.
Figure 3: Dipole-coupled pairs where the right partner is much more shape anisotropic than the left
partner, making the right partner hard and the left partner soft. (a) MFM image after being magnetized by
a magnetic field in the direction of the green vertical arrow and before application of stress. (b) MFM
image after application and removal of stress. The magnetizations of all pairs, expect the one in the upper
right corner show no discernible difference between the pre- and post-stress conditions, but the
magnetization of the soft nanomagnet in the upper right corner (indicated by the short light green arrow)
has rotated by ~1100
.
In order to investigate whether this effect is influenced by dipole coupling between nanomagnets,
we fabricated arrays of closely spaced nanomagnet pairs whose mutual separations are small
enough to allow reasonable dipole coupling between them. One nanomagnet in the pair is
intentionally made much more shape anisotropic than the other. This makes the former
7. magnetically stiff (or hard) and its magnetization cannot be budged by the stress generated
because of the extremely high shape anisotropy energy barrier. The latter has much less shape
anisotropy and hence is softer. Its magnetization state can be affected by stress.
Fig. 3(a) shows the pre-stress MFM images of four such pairs that have all been initially
magnetized with a strong magnetic field to make their magnetizations approximately parallel to
each other. Dipole coupling would prefer anti-parallel ordering within a pair, but the dipole
coupling strength is insufficient to overcome the shape anisotropy energy barrier of any soft
magnet to rotate its magnetization and make the two magnetization orientations in a pair
mutually anti-parallel after the magnetizing field has been removed. Next, all nanomagnets are
compressed along their nominal major axes with an electric field and the field is withdrawn. Fig.
3(b) shows the post-stress MFM images. Three pairs show no perceptible difference between the
initial and final orientations, but the fourth pair in the upper right hand corner shows that the
magnetization of the soft nanomagnet has rotated by a larger angle of ~1100
(> 900
) and once
again the new state is non-volatile. The larger angle of rotation (compared to the case of isolated
nanomagnets) is obviously due to dipole coupling. The latter prefers anti-ferromagnetic ordering
within a pair, i.e., the magnetization of the soft nanomagnet should be anti-parallel to that of the
hard nanomagnet. This is not completely achieved because the magnetization ultimately gets
trapped in a metastable state, but it does not get trapped in a metastable state that is close to the
original state because the dipole coupling is strong enough to dislodge the magnetization from
any such state and steer it to a state subtending a large angle with the original state. The
difference between the isolated and dipole-coupled cases is that in the former, the angular
separation between the old and new states is less than 900
, whereas in the latter, it is greater than
900
. Therefore, the converse magnetoelectric effect is influenced by dipole coupling.
In Fig. 4, we show two more dipole coupled pairs, initially magnetized in the same direction,
where the magnetization of the soft nanomagnet has rotated by ~1500
in one case, and ~1800
in
the other case, after application and withdrawal of stress. Once again the dipole coupling, which
prefers anti-parallel magnetizations of the two magnets, is responsible for the >900
rotation of the
magnetization.
In conclusion, we have demonstrated a non-volatile converse magneto-electric effect in the
nanoscale which is affected by dipole coupling. These results not only show that electric field
control of local magnetization orientation (and hence local magnetic field) is possible, but also
that the effect is non-volatile and can be influenced by neighboring magnetization states because
of dipole coupling. This influence is critical to implement the conditional dynamics of Boolean
(or even non-Boolean) logic where the state of one logic device determines the state of the next.
The dipole-coupled pair, for example, acts as an inverter (NOT gate) which is clocked by the
electric field (the application of the field makes the magnetizations of the partners nearly anti-
parallel, so that if binary bits are encoded in magnetization orientation, then the output bit
becomes the logic complement of the input). Finally, because the magnetization rotation is non-
8. volatile, there are also potential applications in non-volatile memory where bits, encoded in the
magnetization orientation, are written with a voltage.
Figure 4: (a) MFM image of a dipole-coupled pair after being magnetized by a magnetic field in the
direction of the green vertical arrow and before application of stress is shown on the left. In these pairs,
the left partner is more shape-anisotropic than the right, i.e., the left nanomagnet is “hard” and the right
nanomagnet is “soft”. MFM image after application and removal of stress is shown on the right. The
magnetizations of all expect the pair in the upper right corner show no discernible difference between the
pre- and post-stress conditions, but the magnetization of the soft nanomagnet in the upper right corner
(indicated by the short light green arrow) has rotated by ~1500
. (b) Similar to (a), except now the rotation
is by 1800
.
There are challenges however, because clearly the effect is not observed in every fabricated
specimen, but in a minority of specimens. The possible causes for the poor yield are: (i)
lithography imperfections that make the shape anisotropy energy barrier and the potential profile
different in different nanomagnets, (ii) random material defects resulting in pinning sites that trap
the magnetization and prevent its rotation under stress in some nanomagnets, and (iii) multiple
phases in FeGa that spawn different energy barriers and different potential profiles in different
nanomagnets. All this points to a serious challenge; very precise lithography will be required to
translate these observations into a viable technology and material defects need to be mitigated.
9. Nonetheless, because of the extremely low energy dissipation in electric field control of
magnetization [3,4,30,31], these initial observations are encouraging for future energy-efficient
nanomagnetic computing.
ACKNOWLEDGMENTS
This work was supported by the US National Science Foundation under grants ECCS-1124714
and CCF-1216614. The sputtering of FeGa nanomagnets was carried out at the National Institute
of Standards and Technology, Gaithersburg, Maryland, USA.
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Supplementary Material
Fabrication of nanomagnets on poled PMN-PT substrates
The PMN-PT substrates were first poled with an electric field of 8000 V/cm in a direction which
will coincide with the major axes of the nanomagnets (the major axes were nominally parallel to
each other). The poled substrates were spin-coated with two layers of PMMA (e-beam resist) of
different molecular weights in order to obtain superior nanomagnet feature definition: PMMA-
495 Anisol and PMMA-950 Anisol at 2500 rpm spinning rate. The resists were then baked at
1150
C for 2 minutesand exposed in a Hitachi SU-70 SEM with a Nabity attachment using 30 kV
accelerating voltage and 60 pA beam current. Subsequently, the resists were developed in
MIBK:IPA (1:3) for 70 seconds followed by rinsing in cold IPA.
For nanomagnet delineation, a 4-5 nm thick Ti layer was first deposited using e-beam
evaporation at a base pressure of (2-3)× 10-7
Torr, followed by the deposition of 12-17 nm of
FeGa (thickness verified with AFM) using DC magnetron sputtering of a FeGa target with a base
pressure of (2-3)× 10-8
Torr and deposition pressure of 1 mTorr. The magnetron power was 45
W and the deposition was carried out for 45 seconds. The nanomagnets were formed following
lift-off and they were imaged with both scanning electron microscope (SEM) and atomic force
microscope (AFM).
Magnetization states were ascertained with magnetic force microscopy (MFM). All MFM
imaging was carried out with a low moment MFM tip in order to perturb the magnetization states
of the nanomagnets as little as possible.
X-ray diffraction
Grazing incidence and in-plane x-ray diffraction (XRD) were carried out to ascertain the
crystallographic orientation of the grains and compared to data available in the literature. Figure
11. S1 shows the XRD data for the nanomagnets. The film is polycrystalline containing [110], [200]
and [211] oriented grains. The in-plane data indicate <100> textured growth [<110>
texturenormal to the film plane] as also reported in ref. [S1].
Figure S1: The grazing angle and in-plane x-ray diffraction data showing that the sputtered nanomagnets
are polycrystalline with [110], [200] and [211] oriented grains. The in-plane data indicate <110> textured
growth.
X-ray photoelectron spectroscopy
A well-known problem with sputter deposited FeGa films is the variation of Fe and Ga atomic
percent from one layer to another [S1-S3]. To study this compositional variation in our
nanomagnets, we carried out x-ray photoelectron spectroscopy (XPS) by successively removing
layers with Ar ion etching to obtain signal from various layers to ascertain the elemental
composition of each layer. The etching is stopped once we obtain a signal from the substrate (the
substrate was [100]-silicon in this case), indicating that we are approachingthe bottom layer.
Since FeGa oxidizes in air, we get a signal from oxygen. In Figure S2(a) we show the elemental
composition as a function of etch time or layer depth obtained from XPS. In Figure S2(b) we
show the relative abundance of Fe and Ga in each layer after suppressing the oxygen signal. As
expected, the oxygen content is highest at the topmost layer and dwindles as we approach the
bottom (interface with the substrate). The Fe mole fraction also increases with depth. Because of
the compositional variation, we expect the effective magnetostriction to be less than the value
reported for Fe0.8Ga0.2 in the literature.
12. Figure S2: XPS data showing layer by layer composition.
Film morphology
In Figure S3, we show a scanning electron micrograph of the film surface. This is very similar to
that shown in ref. [S1]
Figure S3: Scanning electron micrograph of the film surface showing the morphology.
13. Magnetization studies
The magnetization (M-H) curves were obtained at 77 K and 300 K in a Quantum Design
Vibrating Sample Magnetometer with the magnetic field in-plane and perpendicular-to-plane.
These results are shown in Figure S4. In Figure S5 we zoom in on the low field characteristic at
300 K to determine the coercivity of the film and to examine if there are multiple coercivities
associated with multiple phases. The shape of the curve (there is a broad shoulder) indicates that
there are at least two coercivities associated with different phases. Similar behavior was observed
in ref. [S1].
The presence of multiple coercivities indicates the presence of multiple energy barriers which
will spawn local energy minima and hence metastable states. This is very likely the reason why
metastable states exist and the magnetization gets stuck in one of these states when driven by
stress out of a stable state. In ref. [19], which dealt with an elemental ferrromagnet Co instead of
a compound ferromagnet like FeGa, metastable states were not found and the Co nanomagnets
exhibited a single coercivity. Therefore, the metastable states appear to be a material feature.
From the standpoint of device applications, whether the magnetization is driven by stress to a
stable state or a metastable state is immaterial, as long as the initial and final states are
magnetically distinct.
14. Figure S4: Magnetization curves with the magnetic field in-plane and perpendicular-to-plane. The results
are plotted for two different temperatures.
15. Figure S5: Magnetization curve at low magnetic fields at 77 K and 300 K. The shape of the curve bears
telltale sign of multiple phases with multiple coercivities as observed before in ref. [S1].
16. References
[S1] A. Javed, N. A. Morley and M. R. J. Gibbs, J. Appl. Phys., 107, 09A944 (2010).
[S2] B. Adolphi, J. McCord, M. Bertram, C-G Oertel, U. Merkel, U. Marschner, R. Schäfer, C. Wenzel
and W-J Fischer, Smart Mater. Struct., 19, 055103 (2010).
[S3] A. Javed, N. A. Morley and M. R. J. Gibbs, J. Magn. Magn. Mater., 321, 2877 (2009).