Spin-ordering in S = 1 anisotropic Heisenberg models with nondiagonal spin exchange

TL;DR

This paper investigates the spin ordering in S=1 anisotropic Heisenberg models with nondiagonal exchange, using Monte Carlo methods and semi-classical approximation to explain experimental magnetic behaviors in FeBr2.

Contribution

It introduces a semi-classical Monte Carlo approach to study quantum effects and nondiagonal exchange in S=1 models, linking theory to experimental observations.

Findings

Quantum effects and nondiagonal exchange influence spin ordering.

The model explains the shape of FeBr2's magnetic specific heat.

The model accounts for weakly first-order phase transitions.

Abstract

The properties of S = 1 anisotropic Heisenberg models with nondiagonal exchange between axial and planar spin components are investigated using Monte Carlo techniques. The quantum nature is taken into account in a semi-classical approximation. The ordering of the spins when applying an external field with axial and planar components is discussed. It is argued that the quantum nature of the spins and the nondiagonal exchange may explain the peculiar shape of the magnetic specific heat of FeBr2 as well as the weakly first-order phase transition observed in the same compound when a tilted field is applied.