Phase transitions in a frustrated Ising antiferromagnet on a square lattice

TL;DR

This study investigates phase transitions in a frustrated Ising antiferromagnet on a square lattice, revealing complex transition behaviors and a first-order transition line near a critical ratio of interaction strengths.

Contribution

It provides a detailed analysis of phase transition orders in the frustrated Ising model using effective-field theory with correlations, identifying a first-order transition line near R = -0.5.

Findings

First-order transition line identified near R = -0.5.

Transition behavior differs from previous studies.

Complex phase diagram with multiple transition types.

Abstract

The phase transitions occurring in the frustrated Ising square antiferromagnet with first- ($J_1 < 0$) and second- ($J_2 < 0$) nearest-neighbor interactions are studied within the framework of the effective-field theory with correlations based on the different cluster sizes and for a wide range of $R = J_2/|J_1|$. Despite the simplicity of the model, it has proved difficult to precisely determine the order of the phase transitions. In contrast to the previous effective-field study, we have found a first-order transition line in the region close to $R = -0.5$ not only between the superantiferromagnetic and paramagnetic ($R<-0.5$) but also between antiferromagnetic and paramagnetic ($R>-0.5$) phases.