Electrical detection of magnetization reversal without auxiliary magnets

TL;DR

This paper demonstrates an electrical method to detect magnetization reversal in a relativistic system without auxiliary magnets, using a novel magnetoresistance effect in a (Ga,Mn)As epilayer.

Contribution

It reports the first observation of a magnetoresistance effect enabling electrical detection of magnetization sign without magnetic fields or ferromagnets in a relativistic system.

Findings

Magnetoresistance effect reaches 0.2% at high current density.

Magnetization can be set parallel or antiparallel to spin polarization.

Detection occurs without auxiliary magnetic fields or ferromagnetic reference layers.

Abstract

First-generation magnetic random access memories based on anisotropic magnetoresistance required magnetic fields for both writing and reading. Modern all-electrical read/write memories use instead non-relativistic spin-transport connecting the storing magnetic layer with a reference ferromagnet. Recent studies have focused on electrical manipulation of magnetic moments by relativistic spin-torques requiring no reference ferromagnet. Here we report the observation of a counterpart magnetoresistance effect in such a relativistic system which allows us to electrically detect the sign of the magnetization without an auxiliary magnetic field or ferromagnet. We observe the effect in a geometry in which the magnetization of a uniaxial (Ga,Mn)As epilayer is set either parallel or antiparallel to a current-induced non-equilibrium spin polarization of carriers. In our structure, this linear-in-current magnetoresistance reaches 0.2\% at current density of $10^6$ A cm$^{-2}$.