- The study examines the effect of chromium (Cr) doping on the structure and magneto-transport properties of La0.67Sr0.33MnO3 compounds.
- Polycrystalline samples of La0.67Sr0.33Mn1-xCrxO3 (0≤ x ≥0.10) were prepared and their crystal structure, resistivity, and magnetoresistance were measured.
- X-ray diffraction results showed the crystal structure remained rhombohedral with Cr doping. Resistivity increased and metal-insulator transition temperature decreased with higher Cr content. Magnetoresistance also increased with more Cr doping.
An alternative way to calculate spin ground state of organometallic complexes. Shown for more than one metallic centers and complex formalism, For more please feel free to mail me.
Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
An alternative way to calculate spin ground state of organometallic complexes. Shown for more than one metallic centers and complex formalism, For more please feel free to mail me.
Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Gamry’s eQCM 10M™ is a rapid, impedance-scanning electrochemical quartz crystal microbalance (EQCM) that adds a valuable tool in the analytical toolbox of anyone investigating interfacial processes.
Branislav K. Nikoli
ć
Department of Physics and Astronomy, University of Delaware, U.S.A.
PHYS 624: Introduction to Solid State Physics
http://www.physics.udel.edu/~bnikolic/teaching/phys624/phys624.html
Gamry’s eQCM 10M™ is a rapid, impedance-scanning electrochemical quartz crystal microbalance (EQCM) that adds a valuable tool in the analytical toolbox of anyone investigating interfacial processes.
Branislav K. Nikoli
ć
Department of Physics and Astronomy, University of Delaware, U.S.A.
PHYS 624: Introduction to Solid State Physics
http://www.physics.udel.edu/~bnikolic/teaching/phys624/phys624.html
Vacancy and Copper-doping Effect on Superconductivity for Clathrate MaterialsYang Li
We present a joint experimental and theoretical study of the superconductivity and electronic structures in type-I Cu-doped silicon clathrates and germanium clathrates. The superconducting critical temperature in Ba8Si46–xCux is shown to decrease strongly with copper content increasing. These results are corroborated by CASTEP approach, first-principles simulations calculated from the density-functional theory with plane waves and pseudopotentials. The simulations show that Cu-doping results in a large decrease of electronic density of states in Fermi level, which can explain the superconducting critical temperature decrease with Cu-doping in the BCS theoretical frame. Further, comparison of Ba8Ge46 and Ba8Si46 within the CASTEP approach shows that the superconductivity is an intrinsic property of the sp3 silicon and germanium clathrates without vacancy in the cage framework. By analysis of the density of states (DOS) and reported experimental results of the Zintl-like Ba8Ge43, a new mechanism of vacancy defect is suggested to explain the absence of superconductivity in Ge clathrates, which is of benefit to eliminating the divarication between theoretical prediction and the experimental observation for superconductivity in Ge clathrates. Keeping an entire Si and Ge cage structure without vacancy is the prerequisite for occurrence of superconductivity in clathrates.
Anne marie valente feliciano - nucleation of nb films on cu substratesthinfilmsworkshop
In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. All these along with the quality of the Cu substrate have an important influence on the nucleation and subsequent growth of the Nb film, creating a favorable template for growing the final surface exposed to SRF fields. This contribution shows how the structure and defect density thus electron mean free path (represented by residual resistance ratio values) of Nb films can be tailored on Cu substrates, by varying the ion energy and thermal energy provided to the substrate, favoring the hetero-epitaxial or the fiber growth mode.
Study of Microstructural, Electrical and Dielectric Properties of La0.9Pb0.1M...Scientific Review SR
The present work studies the microstructural and electrical properties of La0.9Pb0.1MnO3 and La0.8Y0.1Pb0.1MnO3 ceramics synthesized by solid-state route method. Microstructure and elemental analysis of both samples were carried out by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) method, respectively. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted structure. The XRD data were further analyzed by Rietveld refinement technique. Raman analysis reveals that Y atom substitutes La site into the LPMO with shifting of phonon modes. The temperature variation of resistivity of undoped and Y-doped La0.9Pb0.1MnO3 samples have been investigated. The electrical resistivity as a function of temperature showed that all samples undergo an metal-insulator (M-I) transition having a peak at transition temperature TMI. Y-doping increases the resistivity and the metal-insulator transition temperature (TMI) shifts to lower temperature. The temperature-dependent resistivity for temperatures less than metal-insulator transition is explained in terms the quadratic temperature dependence and for T > TMI, thermally activated conduction (TAC) is appropriate. Variation of frequency dispersion in permittivity and loss pattern due to La-site substitution in LPMO was observed in the dielectric response curve.
Structural, Electrical and Magnetotransport properties of La0.7Ca0.2Sr0.1MnO3...IOSR Journals
The sample of manganite perovskite oxide La0.7Ca0.2Sr0.1MnO3 has been prepared by solution combustion synthesis. The synthesized sample has been pelletized and further sintered at 8000C for 8 hours. The XRD pattern reveals that the samples are of single phase nature with orthorhombic structure and the diffraction patterns can be indexed with the pbnm space groups. The crystallite sizes calculated from broadening of XRD peaks using Scherrer’s formula were about 18 nm. Resistivity measurements were performed in the temperature range 2K under 3, 5, 10 and 14 T field using PPMS. Magnetoresistance shows a shift in metal-insulator transition temperature from ~213 K at zero field to ~250 K at 14T. MR value decreases as the temperature increases and at 300 K maximum value of MR is found to be ~ 22% for an applied field of 14 T. MR of ~ 28% is observed at 230 K. MR of ~ 35% is observed at 150 K in an applied field of 14 T and MR has negative sign
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.
Mg-doping effect on structural and magnetic properties on two-dimensional tri...Yang Li
Transition metal compounds with two-dimensional triangular lattice, such as LiVO2, are of particular interest, because they exhibit peculiar structural and magnetic behavior involving the frustration present in these oxides. An orbital ordering transition occurs near 500 K, which leads to a suppression of magnetic moment below the phase transition temperature Tt. We synthesized a series of Mg-doped LiVO2 single-phase samples and reported their structural and magnetic properties. The samples were characterized by x-ray diffraction, scanning electron microscope, differential scanning calorimetry, electrical resistivity, magnetic susceptibility, and specific heat measurement. For Mg-doped samples Li1−xMgxVO2 x=0, 0.05, 0.10, and 0.15, the structural analysis show that, with increasing x, the lattice constants change monotonously; in the a-b plane, the lattice expands; while in the c-axis direction, the lattice is compressed. Substitution of Li with Mg ions results in the degeneration of two-dimensional characteristics and the distortion of the VO6 block, which significantly influence magnetic properties. The magnetic phase transition temperature falls with increasing x. The Mg-dopants play an important role on breaking the original moment equilibrium and suppressing the magnetic frustration.
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticlesMai Trần
In recent times perovskite materials are extensively studied and have attracted much attention because they exhibit interesting the properties, showing potential applications in commercial, technical and biomedical. In Vietnam, perovskite materials be of interest research and applications are strong but with major research direction is to go deep into the electrical properties and the magnetic properties. The Lanthanum Strontium manganite is a perovskite-based crystal-structured ceramic material with the formula of La1-xSrxMnO3, where x describes the doping ratio. It has attracted much attention due to its good magnetic, electrical, and catalytic properties and is becoming an attractive possibility material in several biomedical applications, particularly with nano-size. In industry, this material is commonly used in as a cathode material in commercially produced solid oxide fuel cells. In this thesis, we present the Perovskite nanoparticles La1-xSrxMnO3 were successfully synthesized of the nanosize La1-xSrxMnO3 at x = 0; 0.1; 0.2; 0.3 and 0.4 which prepared by a modified sol-gel method. Structure and magnetic properties of them were systematically investigated in dependence on doped Sr ratio x. The structure was investigated by XRD and show slightly changed but magnetic properties varied strongly with changing the doping ratio x. Magnetic properties of samples were studied by Vibrating Sample Mode of Physical Properties Measurement System show at the room temperature, the samples show superparamagnetic properties with high saturated magnetization MS of 57 emu/g which strongly dependents on the doped Sr ratio x.
A Study of Electrical and Magnetic Properties of La+3 Substituted Ni-Zn Ferritesiosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Influence of Interface Thermal Resistance on Relaxation Dynamics of Metal-Die...A Behzadmehr
Nanocomposite materials, including noble metal nanoparticles embedded in a dielectric host medium, are interesting because of their optical properties linked to surface plasmon resonance phenomena. For studding of nonlinear optical properties and/or energy transfer process, these materials may be excited by ultrashort pulse laser with a temporal width varying from some femtoseconds to some hundreds of picoseconds. Following of absorption of light energy by metal-dielectric nanocomposite material, metal nanoparticles are heated. Then, the thermal energy is transferred to the host medium through particle-dielectric interface. On the one hand, nonlinear optical properties of such materials depend on their thermal responses to laser pulse, and on the other hand different parameters, such as pulse laser and medium thermodynamic characterizes, govern on the thermal responses of medium to laser pulse. Here, influence of thermal resistance at particle-surrounding medium interface on thermal response of such material under ultrashort pulse laser excitation is investigated. For this, we used three temperature model based on energy exchange between different bodies of medium. The results show that the interface thermal resistance plays a crucial role on nanoparticle cooling dynamics, so that the relaxation characterized time increases by increasing of interface thermal resistance.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
Study of Raman Scattering in Carbon nanotubesajay singh
Abstract: Present thesis reports the Raman investigation of the Raman scattering in MWNTs as function of laser power. Raman spectra of MWNT were taken at laser parameters (514.5nm, 0.1- 0.6 w). The mathematical analysis of graphitic Raman peaks was done based on Einstein model. Earlier we chose Gaussian and Lorentzian weighting function to investigate Raman graphitic peaks. Earlier we discussed about size dependent Raman scattering in CNTs. When the laser power is increased from a minimum value, it causes the increase in induced temperature in the sample. In this section we have discussed Temperature dependence on Raman spectra. The temperature dependence of linewidth has been interpreted as due to decay of optical phonon into two LA phonons at half optical frequency. Temperature rise in the sample was calculated theoretically as well as experimentally.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Modulus spectroscopy study on Ferroelectric Lithium and Titanium modified Lea...iosrjce
IOSR Journal of Applied Physics (IOSR-JAP) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Similar to Effect of cr doping in structure and magneto transport properties of (la0.67 sr0.33)mno3 (20)
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
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:
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
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.
SAP Sapphire 2024 - ASUG301 building better apps with SAP Fiori.pdfPeter Spielvogel
Building better applications for business users with SAP Fiori.
• What is SAP Fiori and why it matters to you
• How a better user experience drives measurable business benefits
• How to get started with SAP Fiori today
• How SAP Fiori elements accelerates application development
• How SAP Build Code includes SAP Fiori tools and other generative artificial intelligence capabilities
• How SAP Fiori paves the way for using AI in SAP apps
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
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.
Elevating Tactical DDD Patterns Through Object CalisthenicsDorra BARTAGUIZ
After immersing yourself in the blue book and its red counterpart, attending DDD-focused conferences, and applying tactical patterns, you're left with a crucial question: How do I ensure my design is effective? Tactical patterns within Domain-Driven Design (DDD) serve as guiding principles for creating clear and manageable domain models. However, achieving success with these patterns requires additional guidance. Interestingly, we've observed that a set of constraints initially designed for training purposes remarkably aligns with effective pattern implementation, offering a more ‘mechanical’ approach. Let's explore together how Object Calisthenics can elevate the design of your tactical DDD patterns, offering concrete help for those venturing into DDD for the first time!
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.
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.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
GridMate - End to end testing is a critical piece to ensure quality and avoid...ThomasParaiso2
End to end testing is a critical piece to ensure quality and avoid regressions. In this session, we share our journey building an E2E testing pipeline for GridMate components (LWC and Aura) using Cypress, JSForce, FakerJS…
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...
Effect of cr doping in structure and magneto transport properties of (la0.67 sr0.33)mno3
1. Advances in Physics Theories and Applications www.iiste.org
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.19, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
130
Effect of Cr doping in Structure and Magneto-transport
Properties of (La0.67Sr0.33)MnO3
Tejas M. Tank*
, Deepshikha Bhargava, S. P. Sanyal
Solid State Physics Laboratory, Department of Physics, Barkatullah University, Bhopal – 462 026, India
*
E-mail: tejas.physics2020@gmail.com
Abstract
The study of perovskite manganites La0.67Sr0.33Mn1-xCrxO3 (0≤ x ≥0.10) has been carried out. The structure and
magneto-transport properties of La0.67Sr0.33Mn1-xCrxO3 manganites are strongly dependent on the doping level x.
Polycrystalline samples of La0.67Sr0.33Mn1-xCrxO3 (0≤ x ≥0.10) were prepared by solid state reaction method. The
little difference between the ionic radii of Cr3+
and Mn3+
causes no change in the structure, the structure remains
rhombohedral. The temperature dependence of the resistivity is measured from 5 – 400 K without and with
magnetic field upto 5 T. The value of metal-insulator (M-I) transition temperature (TP) decreases when resistivity
increases for all the samples while doping level x increases. The value of magnetoresistance (MR %) increases
with increases Cr doping level for all samples. We have calculated energy band gap (Eg) for all samples and it is
revealed that as per doping level increases Eg increases which is comparable with experimental data. So, the
structure and magneto-transport behavior pretentious by Cr doping.
Keywords: Colossal magnetoresistance, metal-insulator transition.
PACS: 75.47.Gk; 71.30.+h;
INTRODUCTION
The physical properties of the hole doped manganites is one of the most studied topics in the last one
and half decade due to the observation of ‘‘colossal’’ magnetoresistance (CMR) [1]. The basic magnetic and
structural properties of R1-xAxMnO3 (R: rare earth, A: Ca, Ba, Sr) were widely studied in the past. Both end
members – LaMnO3 and AMnO3 – of La1-xAxMnO3 (A = Ca, Sr, Pb, Ba, etc) are antiferromagnetic insulators,
but, doped compounds (0.2 < x < 0.4) exhibit metal-insulator transition in concomitant with the ferromagnetic-
paramagnetic transition. The extraordinary electronic and magnetic properties of colossal magnetoresistance
(CMR) materials R1−xAxMn1−yByO3 (where R is a trivalent rare earth and A is a divalent alkali earth, B is
transition metal) have attracted considerable attention during the past decade. In these perovskite compounds,
interplay between magnetism, charge ordering, and electronic transport have been studied in detail [2]. In
manganites Mn ions play a crucial role in shaping the magnetic properties. Effects of Mn site substitution with
different elements such as Fe, Ni, Co etc. on the TC and other physical properties have been reported by some
workers [3]. We report here a thorough study on the effects of the replacement of Mn by Cr in the colossal
magnetoresistive La0.67Sr0.33MnO3. Replacing trivalent Cr ion with Mn ion provides us a system to understand
weakened double-exchange (DE) interaction (Mn3+
- O- Cr3+
) and the effect of co-doping of electrons on the
system with a network of Mn3+
- O- Cr3+
and Mn4+
- O- Cr4+
. In this paper, we report the results of structural and
transport properties and also energy band gap calculation on La0.67Sr0.33Mn1-xCrxO3 (0≤ x ≥0.10) compounds.
This made it possible to determine change in the electrical transport near the metal- insulator transition in this
compound.
EXPERIMENTAL
Polycrystalline samples of La0.67Sr0.33MnO3 (LSMO), La0.67Sr0.33Mn0.95Cr0.05O3 (LSMCO-5) and
La0.67Sr0.33Mn0.90Cr0.10O3 (LSMCO-10) were synthesized by the solid state reaction method. Stoichiometric
mixture of respective oxide powders was ground and reacted at 1100 ºC for 24 h in air. The samples were
reground, pressed into pellets, heated again and sintered at 1300 ºC for 24 h. The structure and phase purity of
samples were confirmed by Powder X-ray diffraction using Cu Kα radiation at room temperature. The
temperature dependence of the resistivity was measured from 5 – 400 K without and with applied magnetic field
upto 5 T. The magnetic field dependence magnetoresistance carried out at various temperatures.
RESULTS AND DISCUSSION
Figure 1 shows the XRD patterns of La0.67Sr0.33Mn1-xCrxO3 with x=0, 0.05 and 0.10. The XRD analysis
indicates that all samples are single phase with perovskite rhombohedral structure and lattice cell parameters and
unit cell volume are tabulated in Table 1. No impurity phase is observed in the XRD patterns, which suggest that
the doped Cr substitute mainly for Mn. The similarity between the crystal structures of pure and Cr-doped
samples imply that the doped Cr3+
ion does not change the crystalline structure of pure LSMO, which may
mainly result from the similar ionic size of Mn3+
and Cr3+
and the structure remains rhombohedral.
2. Advances in Physics Theories and Applications www.iiste.org
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.19, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
131
TABLE 1. Lattice Parameters and Unit Cell Volume for La0.67Sr0.33Mn1-xCrxO3 samples.
Sample Code Lattice Parameters ( Å ) Unit Cell Volume
(Å)3
a (Å) b (Å) c (Å)
LSMO 5.4797 5.4797 13.4040 402.483
LSMCO-5 5.4767 5.4767 13.3749 401.169
LSMCO-10 5.4741 5.4741 13.3600 400.342
FIGURE 1: X-ray diffraction patterns for La0.67Sr0.33Mn1-xCrxO3 with x=0, 0.05 and 0.10 samples.
Figure 2 demonstrates the temperature dependence of resistivity under 0 T, 1 T, 3 T and 5 T magnetic
fields. When Mn is partly substituted by Cr, the system displays a complicated and interesting transport behavior.
With increasing Cr content, the M–I transition near TP shifts to lower temperature; meanwhile an additional
bump grows up subsequent to it. The coexistence of two bumps of CMR results in CMR remains in a broad
temperature range from the lowest (T2) to above room temperature (T1). The double-peaked feature of ρ-T curve
has been also observed in high doping level (y ≥ 0.07) La0.67A0.33Mn1-yByO3 [4]. In the absence of a magnetic
field LSMCO shows Tmin in the vicinity of 60 K. Assorted possible causes for the low-temperature resistivity
minimum in the LSMCO sample are considered. These include the grain boundary, phase-separation, and
electron-electron localization [5]. To confirm these reasons, work is under process by using theoretical model.
The value of metal-insulator (M-I) transition temperature (TP) decreases when resistivity increases for all the
samples while doping level x increases. The resistivity and TP are listed in Table-2.
TABLE 2. Metal-Insulator Transition Temperature and Resistivity for La0.67Sr0.33Mn1-xCrxO3 samples.
Sample Code M-I Transition (TP) K Resistivity (ρ) Ω*cm
LSMO 373 0.0356
LSMCO-5
351 (T1)
289 (T2)
0.0450
0.0419
LSMCO-10 327 (T1) 0.0548
257 (T2) 0.0506
3. Advances in Physics Theories and Applications www.iiste.org
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.19, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
132
FIGURE 2. Temperature dependence of resistivity of La0.67Sr0.33 Mn1-xCrxO3 with and without magnetic fields.
Therefore, it should be ascribed to the crucial role of Cr. It suggests that Cr element substitution on Mn
site can be a potent way in tuning CMR response. This suggests that it originates from the same mechanism
based on the DE between Mn ions as in undoped La0.67Sr0.33MnO3. As we mentioned that, there is a possibility of
DE through Mn3+
–O–Cr3+
due to the identical electronic configuration between Cr3+
and Mn4+
. The present
results of CMR behavior in La0.67Sr0.33Mn1-xCrxO3 could be supporting evidence to this view. We have calculated
energy bandgap (Eg) of for all samples and it is revealed that as per doping level increases Eg increases which is
comparable with experimental data as well as due to the interruption of well known phenomena of exchange
between Mn3+
and Mn4+
while as the magnetic field increases Eg decreases for each samples which is
theoretically provide evidenced of CMR [6] and Eg values for each samples tabulated in Table 2. One can see
that Cr doping is inefficiency in lowering TP, which imply that there might exist FM interaction between Mn3+
and Cr3+
. Considering those electrical properties, we assume that a FM interaction between Cr3+
and Mn3+
is
similar to the traditional Mn3+
-O-Mn4+
DE process. Because of the different effect of the crystal field over Mn4+
and Cr3+
, this cause an energetic difference between eg orbital levels of Mn3+
and Cr3+
, which becomes strong
enough to result in that electronic exchange between them that is not equivalent to that between Mn3+
and Mn4+
.
Hence, the DE interaction between Mn3+
and Cr3+
is similar to the DE interaction between Mn3+
and Mn4+
but the
former is weaker than the latter.
4. Advances in Physics Theories and Applications www.iiste.org
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.19, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
133
FIGURE 3: The Temperature vs. MR % for La0.67Sr0.33Mn1-xCrxO3 at various magnetic fields.
Sample
Magnetoresistance
1T 3T 5T
MR% T (K) MR% T (K) MR% T (K)
LSMO
LSMCO-5
LSMCO-10
8
9
11
371
354
327
10
12
13
372
353
327
17
18
20
372
354
327
TABLE 3. Temperature dependent MR % at 1, 3 and 5 T magnetic fields for La0.67Sr0.33Mn1-xCrxO3 samples.
The samples show a significant change in resistance with the applied magnetic field. In other words,
they bear varying amount of MR. We show in Fig. 3, the variation of MR value with applied magnetic field at
different temperatures. It is clear from Fig. 3 that the prominent MR at very low temperature, the low-field (< 1
T) MR for Cr doped samples of about 32 % may be attributed to the intergranular spin polarized tunneling (SPT)
of carriers [7]. Thus, it is noted that, at low temperatures, the grain boundary has a significant contribution to the
electrical resistivity of the bulk sample. This is usually observed in polycrystalline samples and may result from
the grain boundary effect. MR value increases gradually with magnetic field for all samples.
CONCLUSION
In conclusion, Cr doping at Mn site weakened double-exchange interaction is reflected in the
progressive decrease in metal-insulator transition (TP) and transport and magneto transport properties in
manganite and FM interaction between Cr3+
and Mn3+
is similar to the traditional Mn3+
-O-Mn4+
DE process.
ACKNOWLEDGEMENTS
The Authors are thankful to Dr. R. Rawat, Dr. V. Ganesan and Dr. M. Gupta of UGC-DAE CSR, Indore for
help in experimental work and to UGC, New Delhi through the research project (No. F. No. 37-90/2009 (SR))
and Special Assistance Programme (SAP). Tejas M. Tank would like to acknowledge UGC-SAP, New Delhi,
India for award of UGC (SAP) – JRF.
5. Advances in Physics Theories and Applications www.iiste.org
ISSN 2224-719X (Paper) ISSN 2225-0638 (Online)
Vol.19, 2013 - Selected from International Conference on Recent Trends in Applied Sciences with Engineering Applications
134
REFERENCES
1. C. N. R. Rao and B. Raveau, Colossal Magnetoresistance, Charge Ordering and Related Properties and
Manganese Oxides, first ed., World Scientific, Singapore (1998).
2. N. Gayatri, A. K. Raychaudhuri, S. K. Tiwary, R. Gundakaram, A. Arulraj and C. N. R. Rao, Phys. Rev. B
56, 1345 (1997).
3. B Raveau, Phil. Trans. R. Society A 366, 83 (2008).
4. N. Paunović, Z. V. Popović, A. Cantarero, F. Sapina, Science of Sintering 40, 55 (2008).
5. B. L. Altshuler and A. G. Aronov, in Electron-Electron Interaction in Disordered Systems, edited by A. L.
Efros
and M. Pollak, North Holland, Amsterdam (1985).
6. M.F.Thorpe, Physics of Manganites, edited by T. Kalpan and S. Mahanti, New York (2002).
7. H. Y. Hwang, S. W. Cheong and B. Batlogg, Phys. Rev. Letter 77, 2041 (1996).
6. This academic article was published by The International Institute for Science,
Technology and Education (IISTE). The IISTE is a pioneer in the Open Access
Publishing service based in the U.S. and Europe. The aim of the institute is
Accelerating Global Knowledge Sharing.
More information about the publisher can be found in the IISTE’s homepage:
http://www.iiste.org
CALL FOR PAPERS
The IISTE is currently hosting more than 30 peer-reviewed academic journals and
collaborating with academic institutions around the world. There’s no deadline for
submission. Prospective authors of IISTE journals can find the submission
instruction on the following page: http://www.iiste.org/Journals/
The IISTE editorial team promises to the review and publish all the qualified
submissions in a fast manner. All the journals articles are available online to the
readers all over the world without financial, legal, or technical barriers other than
those inseparable from gaining access to the internet itself. Printed version of the
journals is also available upon request of readers and authors.
IISTE Knowledge Sharing Partners
EBSCO, Index Copernicus, Ulrich's Periodicals Directory, JournalTOCS, PKP Open
Archives Harvester, Bielefeld Academic Search Engine, Elektronische
Zeitschriftenbibliothek EZB, Open J-Gate, OCLC WorldCat, Universe Digtial
Library , NewJour, Google Scholar