Universal low-temperature behavior of frustrated quantum antiferromagnets in the vicinity of the saturation field

TL;DR

This paper investigates the universal low-temperature thermodynamic behavior of frustrated quantum antiferromagnets near the saturation field, revealing common features and enhanced magnetocaloric effects through lattice gas models and numerical methods.

Contribution

It introduces a universal description of frustrated antiferromagnets near saturation using lattice gas models of localized magnons, validated by numerical diagonalization.

Findings

Strong variation in low-temperature specific heat near saturation

Maximum in isothermal entropy at saturation field

Enhanced magnetocaloric effect observed

Abstract

We study the low-temperature thermodynamic properties of a number of frustrated quantum antiferromagnets which support localized magnon states in the vicinity of the saturation field. For this purpose we use 1) a mapping of the low-energy degrees of freedom of spin systems onto the hard-core object lattice gases and 2) an exact diagonalization of finite spin systems of up to N=30 sites. The considered spin systems exhibit universal behavior which is determined by a specific hard-core object lattice gas representing the independent localized magnon states. We test the lattice gas description by comparing its predictions with the numerical results for low-lying energy states of finite spin systems. For all frustrated spin systems considered we find a strong variation of the low-temperature specific heat passing the saturation field and a maximum in the isothermal entropy at saturation field resulting in an enhanced magnetocaloric effect.