Monte Carlo Study of Mixed-Spin S=(1/2,1) Ising Ferrimagnets

TL;DR

This study uses Monte Carlo simulations to analyze mixed-spin S=1/2 and S=1 Ising ferrimagnets on square and cubic lattices, revealing the absence of tricritical points in 2D and their presence in 3D, with compensation points only in cubic lattices.

Contribution

It provides the first comprehensive Monte Carlo analysis of mixed-spin ferrimagnets, challenging mean-field predictions and identifying dimensional differences in phase behavior.

Findings

No tricritical point in 2D lattices.

Evidence of tricritical point in 3D lattices.

Line of compensation points in cubic lattices.

Abstract

We investigate Ising ferrimagnets on square and simple-cubic lattices with exchange couplings between spins of values S=1/2 and S=1 on neighbouring sites and an additional single-site anisotropy term on the S=1 sites. Based mainly on a careful and comprehensive Monte Carlo study, we conclude that there is no tricritical point in the two--dimensional case, in contradiction to mean-field predictions and recent series results. However, evidence for a tricritical point is found in the three-dimensional case. In addition, a line of compensation points is found for the simple-cubic, but not for the square lattice.