Continuous Versus First Order Transitions in Compressible Diluted Magnets

TL;DR

This paper investigates how disorder and compressibility influence phase transitions in Ising magnets, revealing that disorder maintains continuous transitions while strong compressibility can induce first-order transitions, with differences among magnetic types.

Contribution

It provides a renormalization group analysis showing disorder preserves continuous transitions, and mean field results identifying a tricritical point dependent on dilution and compressibility.

Findings

Disorder does not change the continuous nature of the transition in disordered systems.

Strong compressibility can induce a first-order transition beyond a tricritical point.

Different behaviors are observed between XY and Heisenberg magnets.

Abstract

The interplay between disorder and compressibility in Ising magnets is studied. Contrary to pure systems in which a weak compressibility drives the transition first order, we find from a renormalization group analysis that it has no effect on disordered systems which keep undergoing continuous transition with rigid random-bond Ising model critical exponents. The mean field calculation exhibits a dilution-dependent tricritical point beyond which, at stronger compressibility the transition is first order. The different behavior of XY and Heisenberg magnets is discussed.