Spin Valve Effect in Self-exchange Biased Ferromagnetic Metal/Semiconductor Bilayers

TL;DR

This study demonstrates a spin valve effect in MnAs/(Ga,Mn)As bilayers due to exchange coupling, with findings showing how layer thickness and separation influence magnetic interactions and magnetoresistance.

Contribution

It reveals the existence of a spin valve effect in self-exchange biased ferromagnetic metal/semiconductor bilayers and analyzes how exchange coupling varies with layer thickness and separation.

Findings

Exchange coupling induces spin valve effect in bilayers.

Magnetoresistance depends on layer thickness and separation.

Exchange bias weakens with increased layer thickness.

Abstract

We report magnetization and magetoresistance measurements in hybrid ferromagnetic metal/semiconductor heterostructures comprised of MnAs/(Ga,Mn)As bilayers. Our measurements show that the (metallic) MnAs and (semiconducting) (Ga,Mn)As layers are exchange coupled, re- sulting in an exchange biasing of the magnetically softer (Ga,Mn)As layer that weakens with layer thickness. Magnetoresistance measurements in the current-perpendicular-to-the-plane geometry show a spin valve effect in these self-exchange biased bilayers. Similar measurements in MnAs/p- GaAs/(Ga,Mn)As trilayers show that the exchange coupling diminishes with spatial separation between the layers.