Mixed Ising ferrimagnets with next-nearest neighbour couplings on square lattices

TL;DR

This paper investigates the phase diagram of mixed Ising ferrimagnets on square lattices with next-nearest neighbor couplings, revealing that antiferromagnetic next-nearest neighbor interactions can induce compensation points, contrary to prior assumptions.

Contribution

It introduces the effect of antiferromagnetic next-nearest neighbor couplings on the phase behavior of mixed Ising ferrimagnets, challenging previous beliefs.

Findings

Next-nearest neighbor couplings can lead to compensation points.

Ground state and Monte Carlo analyses reveal new phase diagram features.

Antiferromagnetic interactions influence critical properties and anomalies.

Abstract

We study Ising ferrimagnets on square lattices with antiferromagnetic exchange couplings between spins of values S=1/2 and S=1 on neighbouring sites, couplings between S=1 spins at next--nearest neighbour sites of the lattice, and a single--site anisotropy term for the S=1 spins. Using mainly ground state considerations and extensive Monte Carlo simulations, we investigate various aspects of the phase diagram, including compensation points, critical properties, and temperature dependent anomalies. In contrast to previous belief, the next--nearest neighbour couplings, when being of antiferromagnetic type, may lead to compensation points.