Monte Carlo Simulation of Ising Models with Dipole Interaction

TL;DR

This paper uses Monte Carlo simulations to explore the low-temperature behavior and domain structures of diluted Ising antiferromagnets with dipole interactions, revealing stable domain configurations and memory effects.

Contribution

It introduces a simulation approach considering long-range dipole interactions to analyze domain structures and memory effects in diluted Ising antiferromagnets.

Findings

Stable antiferromagnetic state below Bc1

Ferromagnetic domains form between Bc1 and Bc2

Domains reappear at original positions after cycling the magnetic field

Abstract

Recently, a new memory effect was found in the metamagnetic domain structure of the diluted Ising antiferromagnet $Fe_x Mg_{1-x} Cl_2$ by domain imaging with Faraday contrast. Essential for this effect is the dipole interaction. We simulate the low temperature behavior of diluted Ising-antiferromagnets by a Monte Carlo simulation considering long range interaction. The metamagnetic domain structure occurring due to the dipole interaction is investigated by graphical representation. In the model considered the antiferromagnetic state is stable for an external magnetic field smaller than a lower boundary $B_{c1}$ while for fields larger than an upper boundary $B_{c2}$ the system is in the saturated paramagnetic phase, where the spins are ferromagnetically polarized. For magnetic fields in between these two boundaries a mixed phase occurs consisting of ferromagnetic domains in an antiferromagnetic background. The position of these ferromagnetic domains is stored in the system: after a cycle in which the field is first removed and afterwards applied again the domains reappear at their original positions. The reason for this effect can be found in the frozen antiferromagnetic domain state which occurs after removing the field.