We have studied the spin-relaxation process in spin superlattice structures, both at zero field (no confining potential) and as a function of applied field (variable confining potential). Evidence of an unexpectedly long hole spin-relaxation time associated with the strain splitting of the valence band has been found. In addition, excitonic spin-relaxation times which are unaffected by the strength of the spin-dependent confining potential were observed. We demonstrate that for excitons, spin flip via the magnetic ion-carrier exchange interaction is not the dominant spin-relaxation mechanism, although it may play a more important role in the case of energetic hot carriers.

• Received 22 April 1992

DOI:https://doi.org/10.1103/PhysRevB.46.4316