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In this work, we propose a new method of particle swarm optimization combined with Monte Carlo simulation (PSO–MC for short) to investigate the magnetic properties of the perovskite LaFeO3 structure described by Ising model. First, we use the particle swarm optimization algorithm to calculate the exchange coupling, and then we use the Monte Carlo method to simulate the effects of the crystal field and the external magnetic field on the magnetization, magnetic susceptibility, entropy, phase transition temperature and internal energy of the perovskite LaFeO3. In addition, the effects of the crystal field and temperature on hysteresis loops of LaFeO3 are studied, and the changes of the coercivity and remanence under different parameters are obtained. This paper also compares the research results with the relevant theoretical and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the ferrimagnetic mixed-spin (3/2, 5/2) Ising model was established to investigate the magnetic and thermodynamic properties of a nanoisland bilayer system with graphene-like structure by Monte Carlo simulation. We have analyzed the magnetization of the system and two sublattices, susceptibility, internal energy and hysteresis loops in detail. We have obtained the phase diagrams of the blocking temperature T B affected by the effects of various physical parameters. The triple hysteresis behavior has been observed, which originates from the competition among various physical parameters. Our results are comparable with those of other theoretical and experimental research. • The ferrimagnetic mixed-spin (3/2, 5/2) graphene-like nanoisland bilayer in the longitudinal magnetic field has been investigated. • Magnetization, susceptibility and internal energy have been discussed. • The phase diagrams of blocking temperature have been obtained under the influence of various physical parameters. • The triple hysteresis behavior have been found for certain physical parameters. [ABSTRACT FROM AUTHOR]

• A ferrimagnetic double-layer core–shell Ising graphene nanoisland was studied in an oscillating magnetic field. • The dynamic order parameter, the susceptibility and the internal energy were discussed by Monte Carlo simulation. • The phase diagrams as well as the multiple-loop hysteresis behaviors were exhibited. • The behaviors of the coercivity and remanence under the influence of various parameters were investigated. By using Monte Carlo simulations, we discuss the dynamic magnetic properties of a double-layer core–shell graphene nanoisland with mixed-spin (2, 5/2) configuration in an oscillating magnetic field. We investigate the influence of exchange couplings, oscillating magnetic field, and temperature on the dynamic magnetic and thermodynamic properties of the system. We obtain the various characteristic curves of the dynamic order parameter, susceptibility, and internal energy as well as hysteresis loops. To better understand the impact of these physical parameters on the phase transition of the system, the phase diagrams are depicted. It should be noticed that the system can exhibit multiple-loop hysteresis behaviors under certain conditions. Besides, we plot the coercivity and remanence of the system under the influence of various parameters. [ABSTRACT FROM AUTHOR]

In this work, we have investigated a ferrimagnetic mixed-spin (2, 5/2) Ising nanoisland with bilayer graphene-like structure within the framework of Monte Carlo simulation. The unique magnetic and thermodynamic behaviors of the system have been revealed under the effects of the Hamiltonian parameters and temperature. We obtain the phase diagrams of the blocking temperatures and discontinuous points. For certain parameters, there are rich multiple-cycle hysteresis behaviors, which is caused by competition among various Hamiltonian parameters. Some results obtained can be compared with other theoretical and experimental studies. • A ferrimagnetic mixed-spin (2, 5/2) graphene-like Ising bilayer nanoisland is proposed. • The magnetization, the susceptibility and the internal energy are studied by Monte Carlo simulation. • Effects of next-nearest-neighbor and next-next-nearest-neighbor intralayer exchange couplings are investigated. • The phase diagrams of the blocking temperatures and discontinuous points in different parameter planes are obtained. • Multiple-cycle hysteresis loops behaviors are discovered for certain values of physical parameters. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a ferrimagnetic mixed-spin (1, 3/2) Ising model to describe the ladder-like graphene nanoribbon. Using the Monte Carlo simulation, the effects of the anisotropies, exchange couplings, longitudinal magnetic field and temperature on the magnetic and thermodynamic properties were investigated. Typical temperature dependences of thermodynamics quantities such as magnetization, susceptibility and internal energy were presented under the influence of various physical parameters. The phase diagrams of blocking temperature were obtained in the different parameter planes. In particular, we also found some interesting double hysteresis loops behavior for certain physical parameters. Our results are consistent with those obtained by some theoretical and experimental researches. • The ferrimagnetic mixed-spin (1, 3/2) Ising ladder-like graphene nanoribbon in the longitudinal magnetic field has been studied. • Magnetization, susceptibility and internal energy have been discussed. • The phase diagrams of the blocking temperature under the influence of different parameters have been obtained. • The double hysteresis loops behavior has been found for certain physical parameters. [ABSTRACT FROM AUTHOR]

The Monte Carlo simulation has been applied to study the magnetic behaviors of a ferrimagnetic mixed-spin (1, 2, 5/2) Ising nanoisland with bilayer hexagonal core-shell structure in an external longitudinal magnetic field. We have investigated the influences of the anisotropies, the exchange couplings, the longitudinal field and temperature on magnetization, susceptibility, internal energy and hysteresis loop of the present nanoisland. The behavior of the X parameter (the magnetization, susceptibility, internal energy and blocking temperature) as a function of the parameter is studied. Particularly, the multiple hysteresis loop behaviors have been discovered, such as triple, quintuple, septuple, ninefold and elevenfold hysteresis loops under certain physical parameters. • A ferrimagnetic mixed-spin (1, 2, 5/2) Ising nanoisland with bilayer hexagonal core-shell structure is proposed. • The magnetization, the susceptibility and the internal energy are studied by Monte Carlo simulation. • The phase diagrams of the blocking temperature in different parameter planes are obtained. • The multiple hysteresis loop behaviors are found for certain values of physical parameters. [ABSTRACT FROM AUTHOR]