Spin fluctuations and magnetic polaron formation in dilute magnetic semiconductor quantum well structures

Abstract

Previous work has shown that, in the presence of sp-d exchange between carriers and localized spins in a dilute magnetic semiconductor (DMS), spin fluctuations can give rise to an exchange induced pair interaction between an electron and hole making up an exciton complex, leading to the formation of an excitonic magnetic polaron i.e. magnetically stabilized state). This is in contrast to earlier magnetic polaron treatments which have not explicitly considered fluctuations of the localized spins, but rather only diagonal terms in the exchange interactions or fluctuations of the average magnetization. It is of interest to know what is the form and effect of this interaction in a quantum well (QW) structure. In this paper, we have derived the form of this interaction for a QW and found the energies for the formation of interface spin polaron states for (001) and (111) QW's (for CdMnTe/ CdTe). We have taken into account the effect of strain on the band offsets and on the mass anisotropy of the holes.