Dynamic hysteresis and compensation behaviors of the bilayer Blume–Capel model under an oscillating magnetic field

2019 ◽  
Vol 33 (30) ◽  
pp. 1950369 ◽  
Author(s):  
Mehmet Bati
Keyword(s):  
Magnetic Field ◽  
Crystal Field ◽  
Mean Field ◽  
Field Approximation ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Dynamic Compensation ◽  
Compensation Behavior ◽  
Oscillating Magnetic Field ◽  
Hysteresis Characteristics

Dynamic compensation and hysteresis characteristics of Blume–Capel (BC) model under an oscillating magnetic field have been studied within the dynamic mean field approximation. Spin-1 ferro-antiferromagnetic system Hamiltonian contains bilinear and crystal-field interactions in the presence of a time-dependent oscillating external magnetic field on a bilayer square lattice. Benefiting from the thermal variations of the total magnetization, we find the L-, Q-, R- and S-type compensation behaviors in the system. According to our results, the system does not represent dynamic compensation behavior when it only includes one interaction parameter. We found that the existence of compensation temperatures and hysteresis properties strongly depends on crystal field interactions. It has also been shown that for the paramagnetic phase of the system, single hysteresis behaviors may occur. Finally, the obtained results are compared with some experimental and theoretical results and found in a qualitatively good agreement.

scholarly journals The Combined Effect of Rotation and Magnetic Field on Finite-Amplitude Thermal Convection

1973 ◽  
Vol 26 (5) ◽  
pp. 617 ◽  
Author(s):  
R Van der Borght ◽  
JO Murphy
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Field Approximation ◽  
Finite Amplitude ◽  
Combined Effect ◽  
Mean Field Approximation ◽  
Free Boundaries ◽  
Wide Range ◽  
The Mean ◽  
Basic Equations

The combined effect of an imposed rotation and magnetic field on convective transfer in a horizontal Boussinesq layer of fluid heated from below is studied in the mean field approximation. The basic equations are derived by a variational technique and their solutions are then found over a wide range of conditions, in the case of free boundaries, by numerical and analytic techniques, in particular by asymptotic and perturbation methods. The results obtained by the different techniques are shown to be in excellent agreement. As for the linear theory, the calculations predict that the simultaneous presence' of a magnetic field and rotation may produce conflicting tendencies.

Particle Orientational Properties and Viscosity of a Dense Colloidal Dispersion Composed of Ferromagnetic Spherocylinder Particles: Analysis by Means of Mean Field Approximation for a Simple Shear

2005 ◽  
Author(s):  
Akira Satoh
Keyword(s):  
Magnetic Field ◽  
Applied Magnetic Field ◽  
Mean Field ◽  
Magnetic Interaction ◽  
Colloidal Dispersion ◽  
Field Approximation ◽  
Magnetic Interactions ◽  
Mean Field Approximation ◽  
Particle Interactions ◽  
Orientational Distribution

We have theoretically investigated the particle orientational distribution and viscosity of a dense colloidal dispersion composed of ferromagnetic spherocylinder particles under circumstances of an applied magnetic field. The mean field approximation has been applied to take into account the magnetic interactions of the particle of interest with the other ones which belong to the neighboring clusters, besides its own cluster. The basic equation of the orientational distribution function, which is an integro-differential equation, has approximately been solved by Galerkin’s method and the method of successive approximation. Even when the magnetic interaction between particles is of the order of the thermal energy, the effect of particle-particle interactions on the orientational distribution comes to appear more significantly with increasing the volumetric fraction of particles. This effect comes to appear more significantly when the influence of the applied magnetic field is not relatively so strong compared with magnetic particle-particle interactions.

PULSED SUPERRADIANT EMISSION FROM A MAGNETIC DIPOLE SYSTEM

1993 ◽  
Vol 07 (12) ◽  
pp. 2353-2365
Author(s):  
SALOMON S. MIZRAHI ◽  
MAURO A. MEWES
Keyword(s):  
Magnetic Field ◽  
Single Particle ◽  
Mean Field ◽  
Field Approximation ◽  
Transverse Magnetic ◽  
Time Dependent ◽  
Mean Field Approximation ◽  
Magnetic Dipoles ◽  
Emission Process ◽  
Dipole System

The superradiant emission is considered for a radiating system constituted by N dressed spin-1/2 magnetic dipoles, described by a nonlinear single particle Hamiltonian that is derived under a mean field approximation. This Hamiltonian describes adequately the transient regime of the emission process: The intensity of the radiation follows the sech2 law and its peak is proportional to N2. Then, one considers the application of a periodic time-dependent transverse magnetic field and we study the behavior of the emission that becomes periodically pulsed.

scholarly journals DYNAMICAL MODEL FOR VIRUS SPREAD

Fractals ◽  
1996 ◽  
Vol 04 (02) ◽  
pp. 113-122 ◽  
Author(s):  
G. CAMELO-NETO ◽  
S. COUTINHO
Keyword(s):  
Steady State ◽  
Mean Field ◽  
Field Approximation ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Model Parameters ◽  
Viral Spread ◽  
Infected Cells ◽  
The Mean ◽  
Density Population

The steady state properties of the mean density population of infected cells in a viral spread is simulated by a general forest like cellular automaton model with two distinct populations of cells (permissive and resistant ones) and studied in the framework of the mean field approximation. Stochastic dynamical ingredients are introduced into this model to mimic cells regeneration (with probability p) and to consider infection processes by other means than contiguity (with probability f). Simulations are carried out on a L×L square lattice taking into consideration the eighth first neighbors. The mean density population of infected cells (Di) is measured as a function of the regeneration probability p, and analyzed for small values of the ratio f/p and for distinct degrees of cell resistance. The results obtained by a mean field like approach recovers the simulations results. The role of the resistant parameter R (R≥2) on the steady state properties, is investigated and discussed in comparison with the R=1 monocell case which corresponds to the self organized critical forest model. The fractal dimension of the dead cells ulcers contours was also estimated and analyzed as a function of the model parameters.

Influences of Magnetic Particle-Particle Interactions on Orientational Distributions and Rheological Properties of a Semi-Dense Colloidal Dispersion Composed of Rod-Like Hematite Particles: Analysis by Means of Mean Field Approximation for an External Magnetic Field Parallel to the Angular Velocity Vector of a Simple Shear Flow

2007 ◽  
Author(s):  
Ryo Hayasaka ◽  
Masayuki Aoshima ◽  
Toshinori Suzuki ◽  
Akira Satoh
Keyword(s):  
Magnetic Field ◽  
Magnetic Moment ◽  
Mean Field ◽  
Field Approximation ◽  
Field Direction ◽  
Magnetic Interactions ◽  
Mean Field Approximation ◽  
Magnetic Field Direction ◽  
Orientational Distribution ◽  
The Magnetic Field

We have investigated mainly the influences of magnetic particle-particle interactions on orientational distributions and viscosity of a semi-dense dispersion, which is composed of rod-like particles with a magnetic moment magnetized normal to the particle axis. In addition, the influences of the magnetic field strength, shear rate, and random forces on the orientational distribution and rheological properties have been clarified. The mean field approximation has been applied to take into account magnetic interactions between rod-like particles. The basic equation of the orientational distribution function has been derived from the balance of torques and solved by the numerical analysis method. The results obtained here are summarized as follows. For a strong magnetic field, the rotational motion of the rod-like particle is restricted in a plane normal to the shearing plane because the magnetic moment of the particle is restricted in the magnetic field direction. Under circumstances of a very strong magnetic interaction between particles, the magnetic moment is strongly restricted in the magnetic field direction, so that the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. For a strong shear flow, a directional characteristic of rod-like particles is enhanced, and this leads to a more significant one-peak-type distribution of the orientational distribution function. Magnetic interactions between particles do not contribute to the viscosity because the mean-field vector has only a component along the magnetic field direction.

scholarly journals Stochastic Spatial Model of Producer-Consumer Systems on the Lattice

2013 ◽  
Vol 45 (4) ◽  
pp. 1157-1181 ◽  
Author(s):  
N. Lanchier
Keyword(s):  
Spatial Model ◽  
Initial Density ◽  
Mean Field ◽  
Field Approximation ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Ecological Communities ◽  
Parameter Region ◽  
Dominant Type ◽  
The Individual

The objective of this paper is to give a rigorous analysis of a stochastic spatial model of producer-consumer systems that has been recently introduced by Kang and the author to understand the role of space in ecological communities in which individuals compete for resources. Each point of the square lattice is occupied by an individual which is characterized by one of two possible types, and updates its type in continuous time at rate 1. Each individual being thought of as a producer and consumer of resources, the new type at each update is chosen at random from a certain interaction neighborhood according to probabilities proportional to the ability of the neighbors to consume the resource produced by the individual to be updated. In addition to giving a complete qualitative picture of the phase diagram of the spatial model, our results indicate that the nonspatial deterministic mean-field approximation of the stochastic process fails to describe the behavior of the system in the presence of local interactions. In particular, we prove that, in the parameter region where the nonspatial model displays bistability, there is a dominant type that wins regardless of its initial density in the spatial model, and that the inclusion of space also translates into a significant reduction of the parameter region where both types coexist.

scholarly journals Collective in-plane magnetization in a two-dimensional XY macrospin system within the framework of generalized Ott–Antonsen theory

2020 ◽  
Vol 378 (2171) ◽  
pp. 20190259 ◽  
Author(s):  
Irina V. Tyulkina ◽  
Denis S. Goldobin ◽  
Lyudmila S. Klimenko ◽  
Igor S. Poperechny ◽  
Yuriy L. Raikher
Keyword(s):  
Magnetic Moments ◽  
Mean Field ◽  
Ferromagnetic State ◽  
Dipole Interaction ◽  
Field Approximation ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Two Dimensional ◽  
Stripe Structure ◽  
First Order Phase

The problem of magnetic transitions between the low-temperature (macrospin ordered) phases in two-dimensional XY arrays is addressed. The system is modelled as a plane structure of identical single-domain particles arranged in a square lattice and coupled by the magnetic dipole–dipole interaction; all the particles possess a strong easy-plane magnetic anisotropy. The basic state of the system in the considered temperature range is an antiferromagnetic (AF) stripe structure, where the macrospins (particle magnetic moments) are still involved in thermofluctuational motion: the superparamagnetic blocking T b temperature is lower than that ( T af ) of the AF transition. The description is based on the stochastic equations governing the dynamics of individual magnetic moments, where the interparticle interaction is added in the mean-field approximation. With the technique of a generalized Ott–Antonsen theory, the dynamics equations for the order parameters (including the macroscopic magnetization and the AF order parameter) and the partition function of the system are rigorously obtained and analysed. We show that inside the temperature interval of existence of the AF phase, a static external field tilted to the plane of the array is able to induce first-order phase transitions from AF to ferromagnetic state; the phase diagrams displaying stable and metastable regions of the system are presented. This article is part of the theme issue ‘Patterns in soft and biological matters’.

scholarly journals Comparison of several tetrahedra-based lattices

2001 ◽  
Vol 79 (11-12) ◽  
pp. 1353-1357 ◽  
Author(s):  
M Elhajal ◽  
B Canals ◽  
C Lacroix
Keyword(s):  
Energy Spectrum ◽  
Mean Field ◽  
Field Approximation ◽  
Unit Cell ◽  
Low Energy ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Effective Hamiltonian ◽  
Tetrahedral Unit

A comparison of the quantum Heisenberg anti-ferromagnetic model on the pyrochlore lattice, the checkerboard lattice, and the square lattice with crossing interactions is performed. The three lattices are constructed with the same tetrahedral unit cell and this property is used to describe the low-energy spectrum by means of an effective Hamiltonian restricted to the singlet sector. We analyze the structure of the effective Hamiltonian and solve it within a mean-field approximation for the three lattices. PACS No.: 75.10Jm

scholarly journals THE INFLUENCE OF THE MAGNETIC FIELD ON THE PROPERTIES OF NEUTRON STAR MATTER

2007 ◽  
Vol 22 (07n10) ◽  
pp. 623-629 ◽  
Author(s):  
WEI CHEN ◽  
PU-QING ZHANG ◽  
LIANG-GANG LIU
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Neutron Star Matter ◽  
Density Region ◽  
High Density Region ◽  
The Difference ◽  
The Magnetic Field

In the mean field approximation of the relativistic σ-ω-ρ model, the magnetic fields are incorporated, and it's influence on the properties of n-p-e neutron star matter are studied. When the strength of the magnetic field is weaker than ~1018G, the particles' fractions and chemical potentials, matter's energy density and pressure hardly change with the magnetic field; when the strength of the magnetic field is stronger than ~1020G, the above quantities change with the magnetic field evidently. Furthermore, the pressure is studied in both thermodynamics and hydrodynamics. The difference between these two ways exits in the high density region, that is, the thermal self-consistency may not be satisfied in this region if the magnetic field is considered.

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