Femtosecond scattering dynamics in magnetic semiconductor spin superlattices

Spin-dependent dynamics of polarized carriers in a series of ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$SeZnSe superlattice structures are directly observed by time-resolved upconversion photoluminescence spectroscopy at low temperatures. Polarization measurements in small magnetic fields reveal spin-flip scattering of carriers confined within a magnetic quantum well. A marked change in the dynamics is observed with increasing field and subsequent spin superlattice formation. Exciton lifetimes and spin relaxation are seen to be strongly dependent on both the energy and location of spin states in the heterostructure.