ABSTRACT
This chapter describes the theoretical understanding of spin-dependent tunneling. It considers more sophisticated approaches capturing the important physics related to a realistic spin-dependent electronic band structure of magnetic tunnel junctions. The chapter discusses the influence of imperfections on tunneling magnetoresistance (TMR) and the phenomenon of tunneling anisotropic magnetoresistance, which is induced by spin–orbit coupling and is closely related to TMR. The electrons from the filled quasiparticle states of the left ferromagnetic electrode are thus accepted by unfilled states of the same spin of the right electrode. If the two ferromagnetic electrodes are magnetized parallel, the minority spins tunnel to the minority states and the majority spins tunnel to the majority states. Interface imperfections and defects in the barrier may have a strong effect on spin-dependent tunneling due to the mixing of the tunneling channels, as well as resonant transmission through the localized electronic states created by these defects.
