Tunneling Magnetoresistance and Spin Transfer with (Ga, Mn)As

For suficiently thin barriers, typically a few nanometers insulating layer, carriers have a certain finite probability to be detected on the other side of the potential barrier due to the coupling between the evanescent wave functions on each side of the barrier. With the condition that the density of states (DOS) of the electrodes is spin polarized in the case of ferromagnets, and in a simple picture of a tunneling current proportional to the DOS within each spin channel, the transmission probability is spin dependent, that is, depends on the relative orientation of the two magnetizations. This is the so-called TMR effect. Additionally, for tunneling of holes in the valence band of semiconductors, one can expect an influence of the large spin-orbit coupling on the transmission probability through the barrier as well as a possible defiection of the characteristic carrier wavevector leading to the so-called TAMR effects.