Spin transport in diluted magnetic semiconductor superlattices

We are concerned with nonlinear electron transport in magnetically doped II-VI semiconductor multiple quantum wells with the central well doped with Mn. A II-VI compound with Mn substituted at the group II site exhibits large band electron spin splittings at moderately low magnetic fields. We elaborate on a theory of the influence of exchange coupling with Mn ion spins on electric field domain formation and on the sensitivity of this influence to spin-relaxation rates within the quantum wells. The sequential tunneling current as well as the spin polarization in the magnetic well present a complicated behavior due to the interplay between Coulomb interaction, negative differencial conductance associated with resonant tunneling and exchange interaction between the band spin electrons and the local moments. We observe a significant drop of the spin polarization in the magnetic well at the dc bias where the domain wall is located in the magnetic well. At low doping levels conventional semiconductor superlattices exhibit self-sustained oscillations. We analyze the spin dynamics in these superlattices containing magnetic impurities.