scholarly journals Электронные и магнитные свойства сплавов DyFe-=SUB=-4-=/SUB=-Ge-=SUB=-2-=/SUB=- в области фазового перехода

2020 ◽  
Vol 62 (6) ◽  
pp. 823
Author(s):  
М.В. Матюнина ◽  
М.А. Загребин ◽  
В.В. Соколовский ◽  
В.Д. Бучельников
Keyword(s):  
Magnetic Properties ◽  
Mean Field ◽  
Magnetic Ordering ◽  
Exchange Interactions ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Local Spin Density Approximation ◽  
Electronic And Magnetic Properties ◽  
Strong Localization ◽  
The Mean

Abstract The first-principles studies have been performed for the electronic and magnetic properties of DyFe_4Ge_2 alloys near the P 4_2/ mmm – Cmmm phase transition. The calculations are carried out in a local spin density approximation taking into account the Coulomb interaction within the limit of strong localization in a mean field approximation. The electronic and magnetic properties of the tetragonal structure are shown to be weakly changed in the dependence on the Coulomb and exchange interactions and also on the choice of the approximations. In the case of the orthorhombic structure, a change in the parameters of the Coulomb and exchange interactions leads to a change in the magnetic ordering: from the ferromagnetic to ferrimagnetic in the strong localization limit and from the ferromagnetic to paramagnetic in the mean field approximation.

Partially Disordered State in the Frustrated Heisenberg Ferrimagnet

2014 ◽  
Vol 215 ◽  
pp. 55-60 ◽  
Author(s):  
Sergey N. Martynov
Keyword(s):  
Phase Diagram ◽  
Phase Transitions ◽  
Magnetic Phase ◽  
Mean Field ◽  
Exchange Interactions ◽  
Field Approximation ◽  
Magnetic Phase Transitions ◽  
Mean Field Approximation ◽  
The Mean ◽  
Competition Parameter

A model for the description of two-subsystem Heisenberg ferrimagnet with frustrated intersubsystem exchange and competition between exchange interactions in a subsystem is proposed. The conditions of the existence of noncollinear Yafet-Kittel state and partially ordered magnetic structure are investigated. The phase diagram of competition parameter vs temperature is obtained in the mean field approximation. The peculiarities of the succesive magnetic phase transitions are considered.

scholarly journals UNDERSCREENED KONDO NECKLACE

1992 ◽  
Vol 06 (26) ◽  
pp. 1681-1690 ◽  
Author(s):  
P. FAZEKAS ◽  
HAE-YOUNG KEE
Keyword(s):  
Mean Field ◽  
Magnetic Ordering ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Temperature Phase ◽  
Kondo Problem ◽  
Fermion Systems ◽  
Type Interaction ◽  
The Mean ◽  
Low Temperature Phase

It has been suggested recently by Gan, Coleman, and Andrei that studying the underscreened Kondo problem may help to understand the nature of magnetism in heavy fermion systems. Motivated by Doniach’s work on the S=1/2 Kondo necklace, we introduce the underscreened Kondo necklace models with S>1/2. The underscreened Kondo necklace is the simplest lattice model on which the competition between Kondo spin compensation, and magnetic ordering due to an RKKY-type interaction can be examined. We used the mean-field approximation to determine the phase diagram, and found that the low-temperature phase is always an x−y antiferromagnet. This contention is further supported by the derivation of the exact form of the effective Hamiltonian in the limit of very large Kondo coupling: it is found to be an antiferromagnetic x−y model for the residual S−1/2 spins. In general, the degree of moment compensation depends on both the Kondo coupling, and on S.

The Curie Temperature of the Ferroelectric Superlattice Films with Surface Modification

2009 ◽  
Vol 64 (11) ◽  
pp. 723-728
Author(s):  
Bao-Bing Zheng ◽  
Xiao-Yu Kuang ◽  
Shao-Mei Chang ◽  
Ya-Ru Zhao ◽  
Wen-Qiang Li
Keyword(s):  
Surface Modification ◽  
Ising Model ◽  
Mean Field ◽  
Transverse Field ◽  
Exchange Interactions ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Model Parameters ◽  
Transverse Ising Model ◽  
The Mean

We examine the critical behaviour of a finite alternating ferroelectric superlattice based on the transverse Ising model within the framework of the mean-field approximation. The results indicate that the features of the phase diagrams can be greatly modified by changing the transverse Ising model parameters. The transition temperature of alternating superlattice is described as function of the inter- and intra-layer exchange interactions, the strength of the transverse field, the superlattice thickness and the polarizations. In addition, the effects of surface modification on finite superlattices are also studied.

scholarly journals Magnetization of Rare Earth Materials

1974 ◽  
Vol 27 (1) ◽  
pp. 139 ◽  
Author(s):  
AM Stewart
Keyword(s):  
Rare Earth ◽  
Crystal Field ◽  
Conduction Electron ◽  
Mean Field ◽  
Exchange Interactions ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Polarization Effects ◽  
Formal Procedure ◽  
The Mean

The formal procedure is demonstrated for calculating the magnetization of a rare earth material, in the mean field approximation, at arbitrary fields and temperatures when account is taken of crystal-field splittings, interionic exchange interactions and conduction electron polarization effects.

Phase diagrams and magnetic properties of double perovskite Ba2CrMoO6

2015 ◽  
Vol 29 (27) ◽  
pp. 1550174 ◽  
Author(s):  
M. Ait-Tamerd ◽  
B. Abraime ◽  
K. El Maalam ◽  
A. Benyoussef ◽  
A. El Kenz ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Magnetic Properties ◽  
Phase Diagrams ◽  
Mean Field ◽  
Magnetic Behavior ◽  
Double Perovskite ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
The Mean

In this paper, the Monte Carlo simulation (MCS) and the mean field approximation (MFA) methods have been used to study the magnetic properties of double perovskite Ba2CrMoO6 in the framework of the Ising model, which is important for a better understanding of the magnetic behavior of this material. This compound is constituted of two magnetic cubic sublattices: one occupied by Mo[Formula: see text] and other occupied Cr[Formula: see text], the critical exponents and phase diagrams for this compound are determined. The critical behavior, compensation temperature and susceptibility are also determined.

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