Spin-Polarized Tunneling as a probe of (Ga,Mn)As electronic properties

TL;DR

This study investigates the magnetic and tunneling properties of (Ga,Mn)As-based structures, demonstrating how annealing enhances magnetoresistance through increased exchange energy and hole concentration, supported by theoretical phase diagrams.

Contribution

It provides a combined experimental and theoretical analysis of tunneling magnetoresistance in (Ga,Mn)As, estimating key electronic parameters and illustrating their influence on tunneling phenomena.

Findings

Annealing increases magnetization and TMR in (Ga,Mn)As structures.

Estimated exchange energy is approximately 120 meV.

Theoretical phase diagrams relate TMR/TAMR to Fermi energy and spin-splitting.

Abstract

We present magnetic and tunnel transport properties of (Ga,Mn)As/(In,Ga)As/(Ga,Mn)As structure before and after adequate annealing procedure. The conjugate increase of magnetization and tunnel magnetoresistance obtained after annealing is shown to be associated to the increase of both exchange energy $\Delta$$_{exch}$ and hole concentration by reduction of the Mn interstitial atom in the top magnetic electrode. Through a 6x6 band k.p model, we established general phase diagrams of tunneling magnetoresistance (TMR) and tunneling anisotropic magnetoresistance (TAMR) \textit{vs.} (Ga,Mn)As Fermi energy (E$_F$) and spin-splitting parameter (B$_G$). This allows to give a rough estimation of the exchange energy $\Delta$$_{exch}$=6B$_G$$\simeq$120 meV and hole concentration p$\simeq1.10^{20}$cm$^{-3}$ of (Ga,Mn)As and beyond gives the general trend of TMR and TAMR \textit{vs.} the selected hole band involved in the tunneling transport.