  We report on the study of spin-polarized electric currents in diluted
magnetic semiconductor (DMS) quantum wells subjected to an in-plane external
magnetic field and illuminated by microwave or terahertz radiation. The effect
is studied in (Cd,Mn)Te/(Cd,Mg)Te quantum wells (QWs) and (In,Ga)As/InAlAs:Mn
QWs belonging to the well known II-VI and III-V DMS material systems, as well
as, in heterovalent AlSb/InAs/(Zn,Mn)Te QWs which represent a promising
combination of II-VI and III-V semiconductors. Experimental data and developed
theory demonstrate that the photocurrent originates from a spin-dependent
scattering of free carriers by static defects or phonons in the Drude
absorption of radiation and subsequent relaxation of carriers. We show that in
DMS structures the efficiency of the current generation is drastically enhanced
compared to non-magnetic semiconductors. The enhancement is caused by the
exchange interaction of carrier spins with localized spins of magnetic ions
resulting, on the one hand, in the giant Zeeman spin-splitting, and, on the
other hand, in the spin-dependent carrier scattering by localized Mn2+ ions
polarized by an external magnetic field.
