Effects of magnetic ordering on the anisotropy and temperature dependence of the optical conductivity inLaMnO3:A tight-binding approach

2000 ◽  
Vol 61 (20) ◽  
pp. 13545-13559 ◽  
Author(s):  
K. H. Ahn ◽  
A. J. Millis
Keyword(s):  
Temperature Dependence ◽  
Optical Conductivity ◽  
Tight Binding ◽  
Magnetic Ordering

Tight-binding calculation of the optical conductivity in NaxCoO2

2004 ◽  
Vol 132 (1) ◽  
pp. 43-47 ◽  
Author(s):  
T. Sugibayashi ◽  
D.S. Hirashima
Keyword(s):  
Optical Conductivity ◽  
Tight Binding

Optical Absorptions in Metal Sodium: The Temperature Dependence in the Liquid State

1974 ◽  
Vol 29 (3) ◽  
pp. 462-468
Author(s):  
N. C. Haider
Keyword(s):  
Perturbation Theory ◽  
Solid State ◽  
Temperature Dependence ◽  
Electron Density ◽  
Electron Energy ◽  
Density Of States ◽  
Optical Conductivity ◽  
Liquid State ◽  
Present Calculation ◽  
Electron Density Of States

The temperature dependence of optical absorptions in liquid Na is calculated. The electron energy values are obtained to second order in perturbation theory which are then used to determine the electron density of states. The density of states plots show some structure similar to those noted in the solid state. The optical conductivity in the liquid state is found to increase with the temperature as in the solid state. The present calculation for the optical conductivity gives a rather sharp peak around ħ ω = 1.7 eV. These results are in better agreement with the existing experimental results

Crystal Distortions Associated with Magnetic Ordering in the Antiferromagnetic Compound VF2

1970 ◽  
Vol 14 ◽  
pp. 433-440
Author(s):  
W. S. McCain ◽  
D. L. Albright ◽  
W. O. J. Boo
Keyword(s):  
Single Crystal ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Magnetic Ordering ◽  
The Body ◽  
The Other ◽  
Magnetic Interactions ◽  
One Dimensional ◽  
Lattice Constants ◽  
Vanadium Ions

AbstractLattice constants were measured as a function of temperature by single crystal diffracrometry in the temperature range which includes the Néel temperature of VF2(TN= 7°K). The lattice constants of VF2(D4h14=P42m n m) were measured from room temperature down to 4.2°K. In this range rhe tetragonal c-axis contracts 0.58% from 3.2359 Å (RT) to 3.2170 Å (4.2°K). On the other hand, the a-axes show a net expansion of 0.18% from 4.8023 Å (RT) to 4.8110 Å at 4.2°K. The temperature dependence of the lattice constants can be correlated with anisotropy of exchange forces. Vanadium Ions occupy the center and corner positions of the unit cell. Strong magnetic interactions are directed parallel to the c-axis >001< with considerably weaker interactions parallel to the body diagonals >111< The relative strengths of the two exchange integrals are J >001< = 50 J >111<. As a consequence the magnetic ordering is one-dîmensional along the c-axis and the associated distortions arise from the strong magnetic interactions along this axis.

DILUTED FERROMAGNETIC SEMICONDUCTORS — ORIGIN OF MAGNETIC ORDERING AND SPIN-TRANSPORT PROPERTIES

2008 ◽  
Vol 22 (01n02) ◽  
pp. 104-105 ◽  
Author(s):  
TOMASZ DIETL
Keyword(s):  
Diluted Magnetic Semiconductors ◽  
Spin Transport ◽  
Correlation Energy ◽  
Tight Binding ◽  
Spin Current ◽  
Magnetic Ordering ◽  
Exchange Interactions ◽  
Ferromagnetic Phase ◽  
Magnetic Characteristics ◽  
Ferromagnetic Semiconductors

In the first hour of the lecture the present understanding of the origin of exchange interaction and mechanisms leading to ferromagnetic order in diluted magnetic semiconductors will be presented.1 The lecture will start by discussing energy positions of relevant open magnetic shells, including the correlation energy and excitations within the magnetic ions. The origin and magnitude of sp–d exchange interactions will then be described. This will be followed by presenting the physics of indirect exchange interactions between localized spins contrasting magnetic characteristics in the absence and in the presence of free carriers. The Zener and RKKY models of ferromagnetism will be introduced and the role of confinement, dimensionality, and spin-orbit interaction in determining properties of the ferromagnetic phase will be outlined. The second lecture will be devoted to theory of spin transport in layered structures of diluted ferromagnetic semiconductors, emphasizing the issues important for perspective spintronics devices. A recently developed theory,2 which combines a multi-orbital empirical tight-binding approach with a Landauer–Büttiker formalism will be presented. In contrast to the standard kp method, this theory describes properly the interfaces and inversion symmetry breaking as well as the band dispersion in the entire Brillouin zone, so that the essential for the spin-dependent transport Rashba and Dresselhaus terms as well as the tunneling via k points away from the zone center are taken into account. The applicability of this model for the description of tunneling magnetoresistance (TMR), resonant tunneling spectra, spin-current polarization in Esaki-Zener diodes, and domain-wall resistance will be presented. Note from Publisher: This article contains the abstract only.

MAGNETIC SUSCEPTIBILITY OF YRh2

1993 ◽  
Vol 07 (01n03) ◽  
pp. 834-837
Author(s):  
H. YAMADA ◽  
W. STEINER
Keyword(s):  
Magnetic Susceptibility ◽  
Temperature Dependence ◽  
Density Of States ◽  
Phase Structure ◽  
Magnetic Measurements ◽  
Tight Binding ◽  
The Other ◽  
Spin Fluctuations ◽  
Tight Binding Method ◽  
Good Agreement

Magnetic measurements for YRh2 with the cubic Laves phase structure were performed between 4.2 and 600 K. It was observed that the susceptibility shows a very weak temperature dependence and our data are about 40 % larger than the observed one by Loebich and Raub. On the other hand, the temperature dependence of the susceptibility was also estimated theoretically, by using the density-of-states curve calculated in the tight-binding method and by taking into account the effect of spin fluctuations. A good agreement between our observed and calculated results is obtained.

The effect of magnetic ordering on the temperature dependence of the gadolinium bulk band structure

1992 ◽  
Vol 4 (15) ◽  
pp. 3929-3934 ◽  
Author(s):  
Dongqi Li ◽  
Jiandi Zhang ◽  
P A Dowben ◽  
Rong-Tzong Wu ◽  
M Onellion
Keyword(s):  
Band Structure ◽  
Temperature Dependence ◽  
Magnetic Ordering ◽  
Bulk Band

Alteration of the stacked 2π/3 magnetic structure in the triangular lattice anti-ferromagnet LiCrS2

2001 ◽  
Vol 79 (11-12) ◽  
pp. 1427-1432
Author(s):  
A Lafond ◽  
W Henggeler ◽  
H Mutka ◽  
B Ouladdiaf
Keyword(s):  
Transition Temperature ◽  
Critical Temperature ◽  
Solid State ◽  
Elastic Scattering ◽  
Temperature Dependence ◽  
Triangular Lattice ◽  
Magnetic Ordering ◽  
Magnetic Scattering ◽  
Powder Samples ◽  
Anisotropic Interactions

LiCrS2 has magnetic Cr ions with spin S = 3/2 on a triangular lattice. Other researchers (J. Solid State Chem. 3, 590, 1971) concluded that this compound has an anti-ferromagnetic order with a stacked 2π/3 structure below a transition temperature of the order of TN = 50 K. We have re-examined this system with neutron scattering methods on powder samples, paying attention to the temperature dependence of the magnetic scattering. The overall characteristics of the magnetic ordering are in agreement with the earlier study but we have observed significant modifications of the stacked 2π/3 structure well below the critical temperature. The main new features observed on cooling from T = 25 K down to T = 1.5 K are (i) the gradual decrease from 2.5 µB to 2.3 µB of the ordered moment attributed to the 2π/3 structure, (ii) the appearance of new correlations corresponding to a multiplication of the magnetic unit cell, and (iii) the growth of a diffuse elastic scattering component that can be ascribed to a frozen disorder. These observation are not explained in the framework of the standard theoretical treatments concerning the stacked triangular anti-ferromagnet with Heisenberg or slightly anisotropic interactions. PACS Nos.: 75.10Nr, 75.25+z, 75.40Gb

Electronic Properties of Liquid Silicon

1985 ◽  
Vol 63 ◽  
Author(s):  
J. Q. Broughton ◽  
P. B. Allen
Keyword(s):  
Molecular Dynamics ◽  
Fermi Level ◽  
Electronic Properties ◽  
Density Of States ◽  
Optical Conductivity ◽  
Tight Binding ◽  
Liquid Silicon ◽  
Binding Parameters ◽  
Simple Cubic ◽  
Weber Potential

ABSTRACTThe electronic properties of liquid silicon were computed by coupling molecular dynamics and tight binding methods. By employing the Stillinger-Weber potential, atomic configurations of liquid Si at 1740°C were generated by molecular dynamics. Tight binding parameters chosen to fit fcc,bcc, simple cubic and diamond cubic band structures of silicon, were then used to obtain the electronic properties of the system. All states within 10eV of the Fermi level are found to be delocalized, the density of states spectrum similar (but much broadened) to that of diamond cubic silicon and the optical conductivity is found to be almost featureless with no Drude behavior.

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