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

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$120 meV and hole concentration p$\simeq 1.10^{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.

6 pages, 4 figures. submitted to Phys. Rev. B