Numerical Study of a Mixed Ising Ferrimagnetic System

TL;DR

This paper investigates a classical ferrimagnetic model on a square lattice with spins of one-half and one, using numerical methods to analyze phase transitions and compensation points, revealing differences from earlier mean-field predictions.

Contribution

It provides the first exact ground-state calculations and finite-temperature phase diagram for this ferrimagnetic model, challenging previous mean-field results.

Findings

No compensation point at finite temperature with only nearest-neighbor interactions.

Absence of tricritical point at finite temperature.

Contradicts earlier mean-field analysis results.

Abstract

We present a study of a classical ferrimagnetic model on a square lattice in which the two interpenetrating square sublattices have spins one-half and one. This model is relevant for understanding bimetallic molecular ferrimagnets that are currently being synthesized by several experimental groups. We perform exact ground-state calculations for the model and employ Monte Carlo and numerical transfer-matrix techniques to obtain the finite-temperature phase diagram for both the transition and compensation temperatures. When only nearest-neighbor interactions are included, our nonperturbative results indicate no compensation point or tricritical point at finite temperature, which contradicts earlier results obtained with mean-field analysis.