Valery I. Belokon

Monte Carlo simulation of lattice systems with RKKY interaction

Numerical approaches to the study of the magnetic states, properties, and phase transitions in the Ising spin systems with the long-range exchange interaction is presented. The Monte Carlo calculations have been performed for a system of Ising spins on a square lattice with long-range RKKY interaction. It is shown that the Monte Carlo simulation systems RKKY interaction leads to the formation of a complex of the magnetic structure. We compared the results of simulation with experimental images of domain structure of garnet ferrite films.

Magnetic States of Nanoparticles with RKKY Interaction

Conditions of phase transitions in systems of identical ferromagnetic spherical nanoparticles randomly distributed in metal nonmagnetic matrix and superlattices of small number of nanoparticles with the Ruderman-Kittel-Kasuya-Yosida interaction are researched. In the framework of the Ising model the behavior of superspins is well described with the random interaction field method. The alteration of the effective magnetic moment due to the change in volume affects the choice of the magnetic state of the system: ferromagnetic spin glass or antiferromagnetic spin glass. The ground state of superlattice depends on the distance between particles.

Concentration of magnetic transitions in dilute magnetic materials

In this paper the two-sublattice crystalline ferromagnet in the approximation of the Ising model was investigated. In each sub-lattice density of magnetic atoms can vary from 0 to 1. The exchange interactions within each sublattice and between the spins of different sublattices are considered as given. The case of direct exchange was investigated and the conditions for the occurrence of ferromagnetism, antiferromagnetism and ferrimagnetism, depending on the concentration of magnetic atoms in each sublattice were established.

On the possible application of the method of random exchange interaction fields for studying the magnetic properties of the rocks

In this paper, we analyze the method of random exchange interaction fields in combination with the Bette–Peierls approach and explore the possibility of its application to studying the magnetic properties of the rocks. In particular, we discuss the concentration magnetic phase transitions and, as an example, we study the concentration dependences of the Curie point of titanomagnetite, one of the typical natural ferrimagnetics.

Concentration Phase Transitions in Two-Sublattice Magnets

Phase transitions and critical phenomena are investigated within a two-sublattice model. In the framework of the random fields with the exchange interaction method the system of equations is obtained. It allows us to establish conditions under which magnetic phase transitions are possible. Critical concentration of ferromagnetic atoms which is necessary for the existence of ferromagnetic, ferrimagnetic and antiferromagnetic phases is determined.

Self-reversal of magnetization in titanomagnetite: Effective field theory

In this paper, we analyze the self-reversal of magnetization in titanomagnetites as a function of the Ti content and the distribution of Fe3+ to Fe2+ ion transitions in sublattices (which is associated with the law of charge conservation). The dependence of the Curie point on the Ti concentration and the temperature dependence of the mean magnetic moment per iron atom at different Ti concentrations and different cation distributions in sublattices are calculated.

The magnetic states and Labyrinth ordering in 2D lattices of ising spins with RKKY Interaction

The numerical simulation of 2D simple square lattice of Ising superspins, that interact via the Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interaction is performed. It is found, that at low temperatures in the researched systems predominantly realized labyrinth domain structure. The modeled image of magnetization distribution does not coincide with the image of energy distribution. Hysteresis loops of the samples and labyrinth domain structures similarly obtained by Monte Carlo method, are also observed in physical experiments.

Phase Transitions in Magnets with Competing Exchange Interactions

In this investigations the systems of the nanoparticles with competing exchange interactions are considered. The critical concentrations and possible types of magnetic states of particles in the case of direct exchange and RKKY interaction in the framework of the random interaction field method are determined. It is observed that in magnetic materials with the competition of the direct and indirect exchanges changing the type of ordering is possible at the change in the intensity of the indirect exchange under the influence of external factors.