Disorder dependence of the ferromagnetic quantum phase transition

TL;DR

This paper investigates how quenched disorder affects the nature of ferromagnetic quantum phase transitions in metals, predicting suppression of tricritical temperature and providing experimental distinctions.

Contribution

It introduces a theoretical framework describing the coupling of magnetization to fermionic excitations, highlighting disorder's role in changing transition order.

Findings

Disorder suppresses the tricritical temperature T_tc in ferromagnetic metals.

Transition becomes continuous as residual resistivity increases.

Experimental methods are discussed to distinguish this mechanism from others.

Abstract

We quantitatively discuss the influence of quenched disorder on the ferromagnetic quantum phase transition in metals, using a theory that describes the coupling of the magnetization to gapless fermionic excitations. In clean systems, the transition is first order below a tricritical temperature T_tc. Quenched disorder is predicted to suppress T_tc until it vanishes for residual resistivities rho_0 on the order of several microOhmcm for typical quantum ferromagnets. We discuss experiments that allow to distinguish the mechanism considered from other possible realizations of a first-order transition.