Energy levels and optical transition intensities of direct and indirect excitons in diluted magnetic semiconductor double quantum wells were calculated as a function of the structure parameters and magnetic field. The effects arising from magnetic field induced crossing and repulsion of the exciton levels were investigated. Two structures were studied: (Zn, Mn)Se-based and (Cd, Mn)Te-based double quantum wells. In the (Zn, Mn)Se-based system, magnetic field induced level crossing of direct and indirect excitons was found. Above some magnetic field the indirect exciton becomes the lowest excited state of the system, which leads to an increase of the exciton lifetime by several orders of magnitude. In the (Cd, Mn)Te-based system, energy level crossing of excitons localized in the different wells of the structure was found. In this case magnetic field rise leads to transfer of the lowest exciton state from one well to another well of the system.

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The spin-dependent tunneling of electrons through a two barrier semiconductor heterostructure with a semimagnetic layer was investigated. It was shown that the resonant level splitting in the semimagnetic well under an external magnetic field allows achieving a high level of spin polarization of the current flowing through the proposed spin filter. The dependence of the polarization depth on the parameters of the sample was calculated in the two component diffusion transport model.

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