Mixed spin-1/2 and spin-1 Ising ferromagnets on a triangular lattice

TL;DR

This study uses Monte Carlo simulations to analyze critical phenomena in mixed spin-1/2 and spin-1 Ising models on a triangular lattice, revealing standard phase transitions and rare tricritical behavior depending on spin distribution.

Contribution

It provides the first detailed Monte Carlo analysis of mixed spin-1/2 and spin-1 Ising models on a triangular lattice, highlighting different critical behaviors based on spin arrangements.

Findings

Standard Ising universality class phase transitions observed.

No phase transitions between certain magnetic phases at finite temperature.

Identification of a rare example of tricritical behavior in such models.

Abstract

By Monte Carlo simulations we study critical properties of the mixed spin-1/2 and spin-1 Ising model on a triangular lattice, considering two different ways of the spin-value distributions on the three sublattices: $(1/2,1/2,1)$ and $(1/2,1,1)$. In the former case, we find standard Ising universality class phase transitions between paramagnetic and magnetic phases but no phase transitions between two distinct magnetic phases $(\pm 1/2,\pm 1/2,\pm 1)$ and $(\pm 1/2,\pm 1/2,0)$ at any finite temperature, except for some interesting non-critical anomalies displayed by response functions. On the other hand, the latter case turns out to be a rare (or perhaps the only) example of a two-dimensional mixed spin-1/2 and spin-1 Ising model on a standard lattice that displays tricritical behavior.