Finite-temperature properties of frustrated classical spins coupled to the lattice

TL;DR

This study uses Monte Carlo simulations to explore how spin-lattice coupling affects phase transitions in a frustrated classical Heisenberg model, revealing strengthened Ising-like transitions and lattice deformation, with implications for layered magnetic materials.

Contribution

It demonstrates that spin-lattice coupling enhances the Ising-like transition and induces lattice deformation without changing its universality class in a frustrated Heisenberg model.

Findings

Strengthening of the Ising-like phase transition due to spin-lattice coupling.

Lattice deformation from tetragonal to orthorhombic symmetry.

Universality class remains unchanged with spin-lattice coupling.

Abstract

We present extensive Monte Carlo simulations for a classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice coupled to the lattice degrees of freedom. The Ising-like phase transition, that appears for $J_2/J_1>1/2$ in the pure spin model, is strengthened by the spin-lattice coupling, and is accompanied by a lattice deformation from a tetragonal symmetry to an orthorhombic one. Evidences that the universality class of the transition does not change with the inclusion of the spin-lattice coupling are reported. Implications for ${\rm Li_2VOSiO_4}$, the prototype for a layered $J_1{-}J_2$ model in the collinear regime, are also discussed.