Anisotropy effects in a mixed quantum-classical Heisenberg model in two dimensions

TL;DR

This paper investigates the magnetic properties of a two-dimensional mixed spin Heisenberg model with exchange anisotropy, using high temperature expansions and Monte Carlo simulations, to explain the ferromagnetic transition in a specific compound.

Contribution

It provides a detailed analysis of anisotropy effects in a 2D mixed spin Heisenberg model, linking theoretical results to experimental observations of a ferromagnetic transition.

Findings

Weak anisotropy can induce a ferromagnetic transition at 15K.

High temperature expansions and Monte Carlo simulations effectively describe the magnetic behavior.

The transition is likely driven by very subtle anisotropic interactions.

Abstract

We analyse a specific two dimensional mixed spin Heisenberg model with exchange anisotropy, by means of high temperature expansions and Monte Carlo simulations. The goal is to describe the magnetic properties of the compound (NBu_{4})_{2}Mn_{2}[Cu(opba)]_{3}\cdot 6DMSO\cdot H_{2}O which exhibits a ferromagnetic transition at $T_{c}=15K$. Extrapolating our analysis on the basis of renormalisation group arguments, we find that this transition may result from a very weak anisotropy effect.