MAGNETIC-RELAXATION STUDIED BY TRANSIENT REFLECTIVITY IN CD1-XMNXTE

We show that the study of transient reflectivity in diluted magnetic s emiconductors gives access to magnetic relaxation. Magnetization is ca rried out of equilibrium by above-band-gap laser pulse and thermalizat ion of the spin system is probed by time-resolved reflectivity in the free exciton energy range. Spin relaxation times have been measured in Cd1-xMnxTe at liquid-helium temperature for x between 0.16% and 5%. I t is shown that the relaxation times measured are characteristic of sp in-lattice relaxation and that the phonon-bottleneck effect is circumv ented in such experiments. No evidence of Mn2+ spin relaxation due to exchange interaction with photocarriers could be found in the experime ntal conditions investigated.