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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Magnetic Ordering In The Spinel Compound Li[Mn₂₋ₓlix]O₄(X=0, 0.04), John Gaddy, Jagat Lamsal, Marcus Petrovic, Wouter Montfrooij, Alexander Schmets, Thomas Vojta
Magnetic Ordering In The Spinel Compound Li[Mn₂₋ₓlix]O₄(X=0, 0.04), John Gaddy, Jagat Lamsal, Marcus Petrovic, Wouter Montfrooij, Alexander Schmets, Thomas Vojta
Physics Faculty Research & Creative Works
The two B-site ions Mn3+ and Mn4+ in the stoichiometric spinel structure LiMn2O4 form a complex, columnar ordered pattern below the charge-ordering transition at room temperature. On further cooling to below 66 K, the system develops long-range antiferromagnetic order. In contrast, whereas lithium-substituted Li[Mn2−xLix]O4 also undergoes a charge-ordering transition around room temperature, it only displays frozen in short-range magnetic order below ~25-30 K. We investigate to what extent the columnar charge-order pattern observed in LiMn2O4 can account for the measured magnetic ordering patterns in both the pure and Li-substituted (x=0.04) compounds. We conclude that eightfold rings of Mn4+ ions form …
Influence Of The Rare-Earth Element On The Effects Of The Structural And Magnetic Phase Transitions In Cefeaso, Prfeaso And Ndfeaso, Michael A. Mcguire, Raphäel P. Hermann, Athena S. Sefat, Brian C. Sales, Rongying Jin, David Mandrus, Fernande Grandjean, Gary J. Long
Influence Of The Rare-Earth Element On The Effects Of The Structural And Magnetic Phase Transitions In Cefeaso, Prfeaso And Ndfeaso, Michael A. Mcguire, Raphäel P. Hermann, Athena S. Sefat, Brian C. Sales, Rongying Jin, David Mandrus, Fernande Grandjean, Gary J. Long
Chemistry Faculty Research & Creative Works
We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These materials undergo structural phase transitions, spin density wave-like magnetic ordering of small moments on iron and antiferromagnetic ordering of rare-earth moments. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient and magnetoresistance are reported. The magnetic behavior of the materials have been investigated using Mössbauer spectroscopy and magnetization measurements. Transport and magnetic properties are affected strongly by the structural and magnetic transitions, suggesting significant changes in the band structure and/or carrier mobilities occur, and phonon-phonon scattering is …
The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James
The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James
Physics Faculty Research & Creative Works
The effects of Cu-doping on the structural, magnetic, and transport properties of La0.7Sr0.3Mn1xCuxO3 (0<=x<=0.20) have been studied using neutron diffraction, magnetization, and magnetoresistance (MR) measurements. All samples show the rhombohedral structure with the R[overline 3]c space-group from 10 K to room temperature (RT). Neutron diffraction data suggest that some of the Cu ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects the MnO bond length and Mn-O-Mn bond angle resulting from the minimization of the distortion of the MnO6 octahedron. Resistivity measurements show that a metal to insulator transition occurs for the x>=0.15 samples. The x=0.15 sample shows the highest MR([approximate]80%), which might result from the co-existence of Cu3-Cu2+ and the dilution effect of Cu-doping on the double exchange interaction
Coupled Electrical And Magnetic Properties In (La,Sr)Feo3-Δ, X.-D. Zhou, Qingsheng Cai, Jinbo Yang, M. S. Kim, William B. Yelon, William Joseph James, Y.-W. Shin, B. J. Scarfino, Harlan U. Anderson
Coupled Electrical And Magnetic Properties In (La,Sr)Feo3-Δ, X.-D. Zhou, Qingsheng Cai, Jinbo Yang, M. S. Kim, William B. Yelon, William Joseph James, Y.-W. Shin, B. J. Scarfino, Harlan U. Anderson
Materials Science and Engineering Faculty Research & Creative Works
This article is aimed at studying the temperature dependence oxygen nonstoichiometry, magnetic moments, Fe3+ fraction, Néel temperature and conductivity of (La,Sr)FeO3-δ. It is found that the magnetic properties in La0.60 Sr0.40 Fe3-δ is determined by Fe3+ and its concentration, and the conductance is resulted from Fe4+ ions, which act as electron holes. Both of magnetic and electrical properties were directly governed by oxygen nonstoichiometry (δ). when δ=0.2, the compound has maximum Fe3+, the saturation magnetic moments and Néel temperature are 3.8 µB and 410 °C, both at the highest level, …
Study Of The Electronic Structure Of Cafeo₃, Jinbo Yang, M. S. Kim, Qingsheng Cai, X.-D. Zhou, Harlan U. Anderson, William Joseph James, William B. Yelon
Study Of The Electronic Structure Of Cafeo₃, Jinbo Yang, M. S. Kim, Qingsheng Cai, X.-D. Zhou, Harlan U. Anderson, William Joseph James, William B. Yelon
Materials Science and Engineering Faculty Research & Creative Works
We have studied the charge disproportionation phenomenon in CaFeO3 using the local-spin density approximation with the on-site Coulomb interaction parameter U and exchange parameter J. The calculation reveals that the total number of the 3d electrons is about 5.1 for both Fe(1)(Fe5+) and Fe(2)(Fe3+) atoms, and that there are about 0.25 electron holes in the O-2p band. Therefore, the charge disproportionation can be more accurately described as 2d5L(Fe4+)=d5L2(Fe5+)+d5(Fe3+), where L denotes a hole in the oxygen 2p band, instead of 2d4(Fe4+)=d3(Fe5+)+d5(Fe3+). The hybridization between the Fe-3d and O-2p orbitals is stronger for Fe(1) than for Fe(2) due to the shorter …
Exotic Versus Conventional Scaling And Universality In A Disordered Bilayer Quantum Heisenberg Antiferromagnet, Rastko Sknepnek, Thomas Vojta, Matthias Vojta
Exotic Versus Conventional Scaling And Universality In A Disordered Bilayer Quantum Heisenberg Antiferromagnet, Rastko Sknepnek, Thomas Vojta, Matthias Vojta
Physics Faculty Research & Creative Works
We present Monte Carlo simulations of a two-dimensional bilayer quantum Heisenberg antiferromagnet with random dimer dilution. In contrast with exotic scaling scenarios found in other random quantum systems, the quantum phase transition in this system is characterized by a finite-disorder fixed point with power-law scaling. After accounting for corrections to scaling, with a leading irrelevant exponent of ω ≈ 0.48, we find universal critical exponents z = 1.310(6) and ν = 1.16(3). We discuss the consequences of these findings and suggest new experiments.
Electrical And Magnetotransport Properties Of Canted Antiferromagnet Dy₅Si₂Ge₂, R. Nirmala, V. Sankaranarayanan, K. Sethupathi, Zili Chu, William B. Yelon, V. Prasad, A. V. Morozkin, Satish K. Malik, S. V. Subramanyam
Electrical And Magnetotransport Properties Of Canted Antiferromagnet Dy₅Si₂Ge₂, R. Nirmala, V. Sankaranarayanan, K. Sethupathi, Zili Chu, William B. Yelon, V. Prasad, A. V. Morozkin, Satish K. Malik, S. V. Subramanyam
Physics Faculty Research & Creative Works
Summary form only given. Since the giant magnetocaloric effect is encountered in a ferromagnetic Gd5Si2Ge2 alloy near room temperature it is considered as a suitable material for magnetic refrigerator applications. Also a commensurate structural transition occurs at the magnetic transition temperature and there is a good correlation between the crystal structure and magnetic properties. Such observations have triggered numerous experimental studies on similar rare earth alloys and compounds. We have synthesized its Dy- analogue, namely, Dy5Si2Ge2 and have characterized it by means of room temperature X-ray diffraction, ac magnetic susceptibility (15 K - 300 K), electrical resistivity (at zero field …
Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James
Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James
Physics Faculty Research & Creative Works
ErNi5-xCox alloys were prepared by RF induction melting and analyzed using neutron powder diffraction. Rietveld analysis neutron diffraction data indicates the unit cell volume increases with Co content while the a and c lattice parameters show different dependencies on the composition. the Co atoms show higher affinity for the 3g sites than for the 2c sites. the Co sublattice tends to couple antiferromagnetically to the Er sublattice. the easy magnetization direction is along the c axis.