Universality in Voltage-driven Nonequilibrium Phase Transitions

TL;DR

This paper investigates the non-equilibrium ferromagnetic transition in a resistive Stoner ferromagnet under voltage bias, revealing a universal behavior in the transition controlled by temperature and voltage, with implications for spintronics.

Contribution

It introduces a generalized control parameter combining temperature and voltage, enabling a universal description of the non-equilibrium phase transition in ferromagnetic systems.

Findings

Magnetization remains position-independent along the sample at finite bias for flat density of states.

A universal control parameter unifies temperature and voltage effects on the transition.

Charge density varies along the sample, but magnetization does not, within mean-field theory.

Abstract

We consider the non-equilibrium ferromagnetic transition of a mesoscopic sample of a resistive Stoner ferromagnet coupled to two paramagnetic leads. The transition is controlled by either the lead temperature T or the transport voltage V applied between the leads. We calculate the T and V dependence of the magnetization. For systems with a flat density of states we find within mean-field theory that even at finite bias the magnetization does not depend on the position along the sample axis, although the charge density and other quantities do vary. This may be relevant for possible spintronics applications. In addition, we establish a generalized control parameter in terms of T and V which allows for a universal description of the temperature- and voltage-driven transition.