Dynamic mean-field approximation for the random-bond Ising-spin model

1991 ◽  
Vol 43 (16) ◽  
pp. 13638-13640 ◽  
Author(s):  
J. C. Lin
Keyword(s):  
Mean Field ◽  
Field Approximation ◽  
Spin Model ◽  
Mean Field Approximation ◽  
Ising Spin

scholarly journals The Possibility of Many Compensation Points in a Mixed-Spin Ising Ferrimagnetic System

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Hadey K. Mohamad
Keyword(s):  
Free Energy ◽  
Mean Field ◽  
Field Approximation ◽  
Spin Model ◽  
Mean Field Approximation ◽  
Zero Field ◽  
Mixed Spin ◽  
Simple Cubic ◽  
Simple Cubic Lattice ◽  
The Mean

The magnetic properties of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising model with different anisotropies are investigated by using the mean-field approximation (MFA). In particular, the effect of magnetic anisotropies on the compensation phenomenon, acting on A-atoms and B-ones for the mixed-spin model, has been considered in a zero field. The free energy of a mixed-spin Ising ferrimagnetic system from MFA of the Hamiltonian is calculated. By minimizing the free energy, we obtain the equilibrium magnetizations and the compensation points. The phase diagram of the system in the anisotropy dependence of transition temperature has been discussed as well. Our results of this model predict the existence of many (two or three) compensation points in the ordered system on a simple cubic lattice.

THE TRANSVERSE ISING MODEL UNDER A TIME OSCILLATING FIELD

1999 ◽  
Vol 13 (02) ◽  
pp. 207-214 ◽  
Author(s):  
M. SANTOS ◽  
M. J. de OLIVEIRA
Keyword(s):  
Mean Field ◽  
Transverse Field ◽  
Field Approximation ◽  
Quantum Spin ◽  
Monte Carlo Algorithm ◽  
Mean Field Approximation ◽  
Quantum Spin Chains ◽  
Loop Area ◽  
Ising Spin ◽  
Ising Spin System

We have studied an Ising spin system in a transverse field, at zero temperature, under a time oscillating longitudinal field by means of a mean-field approximation and a Monte Carlo algorithm, appropriate to study the ground-state properties of quantum spin chains. For large values of the transverse field Γ or large amplitude h0 of the oscillating field, the magnetization oscillates around a zero value with the same frequency but delayed. Decreasing Γ, at small a h0, the system undergoes a phase transition to a state in which the magnetization oscillates around a nonzero value. We have also obtained the behavior of the hysteresis loop area near the Curie point.

scholarly journals Rare-earth tuned magnetism and magnetocaloric effects in double perovskites R2NiMnO6

2021 ◽  
Author(s):  
Anzar Ali ◽  
Kanika Pasrija ◽  
Gyaneshwar Sharma ◽  
Sanjeev Kumar ◽  
Yogesh Singh
Keyword(s):  
Magnetic Moments ◽  
Mean Field ◽  
Double Perovskite ◽  
Field Approximation ◽  
Spin Model ◽  
Mean Field Approximation ◽  
Ferromagnetic Transition ◽  
Double Perovskites ◽  
Magnetic Entropy ◽  
Perovskite Materials

Abstract We present a comprehensive experimental study of magnetization {\color {blue} ($2 < T < 300$~K, $1 < H < 8$~T)} and magnetocaloric effect in double perovskite materials $R_2$NiMnO$_6$ with $R =$ Pr, Nd, Sm, Gd, Tb, and Dy. While a paramagnetic to ferromagnetic transition, with T$_{\rm C}$ in the range $\sim 100 - 200~$K, is a common feature that can be attributed to the ordering of Mn$^{4+}$ and Ni$^{2+}$ magnetic moments, qualitatively distinct behavior depending on the choice of $R$ is observed at low temperatures. These low-temperature anomalies in magnetization are also manifest in the change in magnetic entropy, $-\Delta S_{M}$, whose sign depends on the choice of $R$. In order to understand these results, we present theoretical analysis based on mean-field approximation and Monte Carlo simulations on a minimal spin model. The model correctly captures the key features of the experimental observations.

A MEAN-FIELD APPROACH TO A DISCRETE DIPOLAR SPIN MODEL WITH UNIAXIAL MAGNETIC ANISOTROPY

2009 ◽  
Vol 20 (09) ◽  
pp. 1335-1343
Author(s):  
YUSUKE TOMITA ◽  
SHUNSUKE YANAI ◽  
HAJIME TAKAYAMA
Keyword(s):  
Magnetic Anisotropy ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Dipolar Interaction ◽  
Field Approximation ◽  
Spin Model ◽  
Lattice Points ◽  
Mean Field Approximation ◽  
Hypercubic Lattice ◽  
Dipolar System

Using the mean-field approximation, we study the reorientation transition in a discrete dipolar spin model. We array the d-dimensional spins in the d-1-dimensional hypercubic lattice points, and apply the magnetic anisotropy in the dth direction. Even though the long-range dipolar interaction is truncated to the nearest-neighbor interaction, the model exhibits the reorientation transition. The effects of the exchange interaction on the dipolar system are also studied.

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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