Spin-polarized transport in dilute magnetic semiconductor tunnel junctions

The author considers transport properties of a trilayer junction consisting of an insulator sandwiched between two dilute magnetic semiconductors (DMSs). The magnetization directions of the two DMSs are not parallel but at a relative angle of theta. After calculating the transmission probabilities, the author calculates the conductance using the Landauer formula. The author defines a ratio R(theta,T), related to the tunneling magnetoresistance, which compares the theta=0 to the theta not equal 0 conductance at temperature T. The author also calculates R(theta,T) semiclassically using the well-known Julliere formula. The author shows that, in general, R(theta,T) obtained from the Julliere formula poorly approximates R(theta,T) obtained from the Landauer formula.