Ising and anisotropic Heisenberg magnets with mobile defects

TL;DR

This paper investigates phase diagrams of 2D Ising and anisotropic Heisenberg models with mobile defects under external fields, revealing defect stripe instability and spin-flop structures through Monte Carlo simulations.

Contribution

It extends previous studies by analyzing phase diagrams of these models in external fields, highlighting the mechanisms behind phase transitions.

Findings

Phase transition in Ising model due to defect stripe instability.

Spin-flop structures are crucial in the Heisenberg model.

Monte Carlo simulations effectively map phase diagrams.

Abstract

Motivated by experiments on (Sr,Ca,La)_14 Cu_24 O_41, a two-dimensional Ising model with mobile defects and a two-dimensional anisotropic Heisenberg antiferromagnet have been proposed and studied recently. We extend previous investigations by analysing phase diagrams of both models in external fields using mainly Monte Carlo techniques. In the Ising case, the phase transition is due to the thermal instability of defect stripes, in the Heisenberg case additional spin-flop structures play an essential role.