Spin depolarization of a ZnCdSe quantum-well spin detector (SD) in ZnMnSe∕ZnCdSe light-emitting quantum structures is investigated by cw and time-resolved optical orientation spectroscopy. It is shown that spin depolarization is governed by three distinct spin relaxation processes with the corresponding polarization decay times of 850, 30, and <10ps. The dominant and the fastest process is attributed to spin relaxation accompanying energy relaxation of hot excitons (and hot carriers) within the SD, providing evidence that it can be an important source of spin loss, leading to the observed limited efficiency of optical spin injection in the structures.

. Pump-probe transient spectroscopy is one of the most powerful methods to discriminate the ultrafast dynamics of the optically prepared e-h plasma, excitons and the subsequent spin dynamics of local magnetic moments [2][3][4]. In this work, we studied the formation and relaxation dynamics of the exciton interacting with the local spin system of magnetic ions in DMS quantum wells (QWs) by using transient pump-probe spectroscopy in magnetic fields. The study reveals the dynamical band-gap renormalization (BGR) due to the exchange-correlation of the dense carriers, the formation of excitonic magnetic polaron (EMP) and the long-lived feature of the spin alignment for the magnetic ions within EMPs.

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