Field induced tricritical behavior in the S=1/2 quasi one-dimensional frustrated Ising antiferromagnet

TL;DR

This study uses Monte Carlo simulations to show how a small magnetic field can induce a transition from XY to tricritical behavior in a quasi-one-dimensional frustrated Ising antiferromagnet, explaining experimental observations.

Contribution

It demonstrates the field-induced crossover from XY to tricritical behavior and links it to quantum exchange effects in S=1/2 systems, providing new insights into phase transitions in frustrated magnets.

Findings

Small applied field causes crossover from XY to tricritical behavior.

Experimental critical exponents align with simulation results.

Quantum exchange mixing explains differences in phase transitions.

Abstract

The results of extensive histogram cluster heat-bath Monte Carlo simulations on the critical behavior of the quasi-one dimensional Ising antiferromagnet on a stacked triangular lattice are presented. A small applied field is shown to induce a crossover from XY universality to mean-field tricritical behavior. Experimental estimates of critical exponents suggest that these two types of phase transitions are observed in S=1 CsNiCl$_3$ and $S=1/2$ CsCoBr$_3$, respectively. The present results demonstrate that this difference can be explained by an unusual staggered magnetic field arising from quantum exchange mixing previously proposed to account for spin excitations in $S=1/2$ quasi-one-dimensional Ising antiferromagnets.