HIERARCHY OF RELAXATION-TIMES IN THE SYSTEM OF MN-ION SPINS IN PHOTOEXCITED SEMIMAGNETIC QUANTUM-WELLS

Energy and spin relaxation in a Mn-ion system has been investigated in (Cd,Mn)Te/(Cd,Mg)Te semimagnetic quantum wells photoexcited by 70-ps laser pulses at the magnetic field B=14 T with the use of a pump-probe technique. An effective (within characteristic time of 0.5 ns) energy transfer from photoexcited carriers to the Mn-ion spin system has bee n established. It leads to the formation of spatial microdomains with an elevated Mb-ion spin temperature. Two strongly different relaxation times tau(1)=4 ns and tau(2)=270 ns were found from the exciton emiss ion line shift. The short one appears in the measurements during the d ecay of the excitons generated with the strong pump pulse and reflects the exciton diffusion from hot microdomains. The long time correspond s to the Mn-spin-lattice relaxation: it has been found from the time d ependence of the energy of the excitons generated with weak probe lase r pulses.