Magnetic Ordering and Phase Separation in Binary Alloys with One Magnetic Component

1982 ◽  
Vol 19 ◽  
Author(s):  
J.L. Moran-Lopez ◽  
Jesus Urias
Keyword(s):  
Phase Separation ◽  
Binary Alloys ◽  
Mean Field ◽  
Magnetic Ordering ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Magnetic Component ◽  
Separation Temperature ◽  
Ferromagnetic Interactions ◽  
Ferromagnetic Ordering

ABSTRACTMagnetic ordering and phase separation in binary alloys with one magnetic component are studied within the mean field approximation. The influence of ferromagnetic ordering on the phase separation temperature (TCS) is examined in detail. In general it is found that magnetism increases TCS and causes strong asymmetries in the phase diagram. In particular, it is found that in systems with only ferromagnetic interactions, the Curie temperature (TCM) and TCS are the same. Results for the phase diagrams and for the temperature dependence of the magnetic and spatial order parameters are presented.

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.

KINETIC ENERGY AND PHASE SEPARATION IN A DOPED ANTIFERROMAGNET

1995 ◽  
Vol 09 (24) ◽  
pp. 1623-1629 ◽  
Author(s):  
XIN XU ◽  
YUN SONG ◽  
SHIPING FENG
Keyword(s):  
Phase Separation ◽  
Kinetic Energy ◽  
Ground State ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Numerical Result ◽  
The Mean ◽  
State Kinetic

The ground-state kinetic energy of the t-J model is studied within the mean field approximation by using the fermion-spin transformation, the results show that the mean field ground-state kinetic energy is close to the numerical result at under dopings, and roughly consistent with the numerical result at optimal dopings. It is also shown that the frustration term J′ is favourable to diminish the range of the phase seperation in the t-J model.

PHASE DIAGRAMS OF THE FCC BLUME–EMERY–GRIFFITHS MODEL ON A CELLULAR AUTOMATON

2007 ◽  
Vol 18 (09) ◽  
pp. 1417-1427 ◽  
Author(s):  
A. ÖZKAN ◽  
B. KUTLU
Keyword(s):  
Cellular Automaton ◽  
Mean Field ◽  
State Diagram ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Face Centered Cubic ◽  
Face Centered ◽  
Creutz Cellular Automaton ◽  
Beg Model ◽  
Ferromagnetic Ordering

The spin-1 Ising (BEG) model has been simulated on a cellular automaton improved from the Creutz cellular automaton (CCA) for a face-centered cubic lattice. The simulations have been made in the 0 ≤ d = D/J ≤ 7 and -1.25 < k = K/J ≤ 0 parameter region. In this region, the ground state diagram (k, d) has ferromagnetic and perfect zero ordering regions. The ferromagnetic ordering region separates into four regions which exhibit different phase transition types as the first order, the second order, the reentrant, the double-reentrant and the successive phase transitions. The simulation results show that the model has the tricritical points, the critical end points and the bicritical points on the (kTC/zJ, d) and (kTC/zJ, k) planes as indicated by the Mean Field approximation results.

scholarly journals LATERAL PHASE SEPARATION OF CONFINED MEMBRANES

2011 ◽  
Vol 25 (03) ◽  
pp. 457-466
Author(s):  
MESFIN ASFAW
Keyword(s):  
Phase Separation ◽  
Phase Behavior ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Critical Potential ◽  
Potential Depth ◽  
Lateral Phase Separation

We consider the membranes interacting via short, intermediate and long stickers. The effects of the intermediate stickers on the lateral phase separation of the membranes are studied via mean-field approximation. The critical potential depth of the stickers increases in the presence of the intermediate sticker. The lateral phase separation of the membrane is thus suppressed by the intermediate stickers. Considering the membranes interacting with short and long stickers, the effect of confinement on the phase behavior of the membranes is also investigated analytically.

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.

scholarly journals Unconventional phase separation in the model 2D spin-pseudospin system

2018 ◽  
Vol 185 ◽  
pp. 11006 ◽  
Author(s):  
K.S. Budrin ◽  
Yu.D. Panov ◽  
A.S. Moskvin ◽  
A.A. Chikov
Keyword(s):  
Monte Carlo ◽  
Phase Separation ◽  
Ground State ◽  
Spin Exchange ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Spin Subsystem ◽  
Monte Carlo Calculations ◽  
Antiferromagnetic Ordering

The competition of charge and spin orderings is a challenging problem for strongly correlated systems, in particular, for high-Tc cuprates. We addressed a simplified static 2D spin-pseudospin model which takes into account both conventional spin exchange coupling and the on-site and inter-site charge correlations. Classical Monte-Carlo calculations for large square lattices show that homogeneous ground state antiferromagnetic solutions found in a mean-field approximation are unstable with respect to phase separation into the charge and spin subsystems behaving like immiscible quantum liquids. In this case, with lowering of a temperature one can observe two sequential phase transitions: first, antiferromagnetic ordering in the spin subsystem diluted by randomly distributed charges, then, the charge condensation in the charge droplets. The inhomogeneous droplet phase reduces the energy of the system and changes the diagram of the ground states. On the other hand, the ground state energy of charge-ordered state in a mean-field approximation exactly matches the numerical Monte-Carlo calculations. The doped charges in this case are distributed randomly over a system in the whole temperature range. Various thermodynamic properties of the 2D spin-pseudospin system are studied by Monte-Carlo simulation.

The Determination of the Magnetoelectric Coupling Coefficient in Ferroelectric–Ferromagnetic Composite Based on PZT–Ferrite

2013 ◽  
Vol 58 (4) ◽  
pp. 1401-1403 ◽  
Author(s):  
J.A. Bartkowska ◽  
R. Zachariasz ◽  
D. Bochenek ◽  
J. Ilczuk
Keyword(s):  
Dielectric Permittivity ◽  
Coupling Coefficient ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Magnetoelectric Coupling ◽  
Mean Field Approximation ◽  
Dielectric Measurements ◽  
Temperature Dependences ◽  
Multiferroic Composite

Abstract In the present work, the magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the multiferroic composite was determined. The research material was ferroelectric-ferromagnetic composite on the based PZT and ferrite. We investigated the temperature dependences of the dielectric permittivity (") for the different frequency of measurement’s field. From the dielectric measurements we determined the temperature of phase transition from ferroelectric to paraelectric phase. For the theoretical description of the temperature dependence of the dielectric constant, the Hamiltonian of Alcantara, Gehring and Janssen was used. To investigate the dielectric properties of the multiferroic composite this Hamiltonian was expressed under the mean-field approximation. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.

scholarly journals Hexagonal-Shaped Spin Crossover Nanoparticles Studied by Ising-Like Model Solved by Local Mean Field Approximation

2021 ◽  
Vol 7 (5) ◽  
pp. 69
Author(s):  
Catherine Cazelles ◽  
Jorge Linares ◽  
Mamadou Ndiaye ◽  
Pierre-Richard Dahoo ◽  
Kamel Boukheddaden
Keyword(s):  
Spin Crossover ◽  
Hexagonal Lattice ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Ligand Field ◽  
Order And Disorder ◽  
The Matrix ◽  
Local Mean ◽  
Parameter Values

The properties of spin crossover (SCO) nanoparticles were studied for five 2D hexagonal lattice structures of increasing sizes embedded in a matrix, thus affecting the thermal properties of the SCO region. These effects were modeled using the Ising-like model in the framework of local mean field approximation (LMFA). The systematic combined effect of the different types of couplings, consisting of (i) bulk short- and long-range interactions and (ii) edge and corner interactions at the surface mediated by the matrix environment, were investigated by using parameter values typical of SCO complexes. Gradual two and three hysteretic transition curves from the LS to HS states were obtained. The results were interpreted in terms of the competition between the structure-dependent order and disorder temperatures (TO.D.) of internal coupling origin and the ligand field-dependent equilibrium temperatures (Teq) of external origin.

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