The Origin and Control of the Sources of AMR in (Ga,Mn)As Devices

TL;DR

This study investigates the origins and control mechanisms of anisotropic magnetoresistance in ultra-thin (Ga,Mn)As layers, combining experimental separation of AMR components with theoretical modeling to understand and engineer AMR behavior.

Contribution

It introduces new experimental methods to isolate AMR components and extends theoretical analysis with a simplified model explaining the non-crystalline AMR origin.

Findings

Non-crystalline AMR sign depends on spin-orbit coupling form.

AMR components can be engineered via lithography-induced lattice relaxations.

Theoretical model clarifies the role of impurity potential in AMR.

Abstract

We present details of our experimental and theoretical study of the components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As. We develop experimental methods to yield directly the non-crystalline and crystalline AMR components which are then independently analyzed. These methods are used to explore the unusual phenomenology of the AMR in ultra thin (5nm) (Ga,Mn)As layers and to demonstrate how the components of the AMR can be engineered through lithography induced local lattice relaxations. We expand on our previous [Phys. Rev. Lett. \textbf{99}, 147207 (2007)] theoretical analysis and numerical calculations to present a simplified analytical model for the origin of the non-crystalline AMR. We find that the sign of the non-crystalline AMR is determined by the form of spin-orbit coupling in the host band and by the relative strengths of the non-magnetic and magnetic contributions to the impurity potential.