Regensburg 2007 – wissenschaftliches Programm

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SYSS: Symposium Spins in Semiconductors

SYSS 1: Spins in Semiconductors

SYSS 1.8: Hauptvortrag

Montag, 26. März 2007, 12:00–12:20, H1

Tunnel Anisotropic Magneto Resistance - TAMR — •Laurens Molenkamp — Physikalisches Institut (EP 3), Universität Würzburg

In the ferromagnetic semiconductor (Ga,Mn)As, we have found a novel magnetoresistance effect, dubbed tunnel anisotropic magnetoresistance (TAMR), The effect is due to the strong spin-orbit coupling in the material, which results in an equally strong dependence of the density of states on magnetization direction. The effect leads to the observation of a spin valve-like behavior in tunnel structures containg a single ferromagnetic layer and also dominates the spin-valve signal obtained from structures containing two (Ga,Mn)As layers. While the effect usually amounts to severals tens of percent in amplitude, at low temperatures resistance changes of five orders of magnitude. This is caused by the fact that the system undergoes a metal-insulator transition upon reorientation of the magnetization. I will present a detailed calculation of the Mn impurity states involved in the metal-insulator transition.

At the end of the talk, I will briefly discuss some recent related work in our group. We have learned how to tailor the magnetic anisotropies of (Ga,Mn)As-based nanostructures and demonstrate a simple memory element based upon this technique.