Nonequilibrium Multiple Transitions in the Core-shell Ising Nanoparticles Driven by Randomly Varying Magnetic Fields

TL;DR

This study uses Monte Carlo simulations to explore how a core-shell Ising nanoparticle responds to randomly varying magnetic fields, revealing multiple nonequilibrium phase transitions driven by field width and temperature.

Contribution

It introduces a detailed analysis of nonequilibrium multiple transitions in core-shell nanoparticles under stochastic magnetic fields, highlighting the effects of system parameters.

Findings

Identification of dynamical symmetry breaking transitions.

Observation of multiple nonequilibrium phase transitions.

Phase diagrams showing temperature and field width dependence.

Abstract

The nonequilibrium behaviour of a core-shell nanoparticle has been studied by Monte- Carlo simulation. The core consists of Ising spins of $\sigma=1/2$ and the shell contains Ising spins of $S=1$. The interactions within the core and in the shell are considered ferromagnetic but the interfacial interaction between core and shell is antiferromagnetic. The nanoparticle system is kept in open boundary conditions and is driven by randomly varying (in time but uniform over the space) magnetic field. Depending on the width of the randomly varying field and the temperature of the system, the core, shell and total magnetization varies in such a manner that the time averages vanish for higher magnitude of the width of random field, exhibiting a dynamical symmetry breaking transitions. The susceptibilities get peaked at two different temperatures indicating nonequilibrium multiple transitions. The phase boundaries of the nonequilibrium multiple transitions are drawn in the plane formed by the axes of temperature and the width of the randomly varying field. Furthermore, the effects of the core and shell thicknesses on the multiple transitions have been discussed.