Ultrafast Spin Relaxation and Dynamics of Carriers in Diluted Magnetic Semiconductor Quantum Wells

Spin dynamics of carriers in multiple quantum wells of Cd0.95Mn0.05Te has been studied by the transient pump-probe absorption spectroscopy in magnetic field. The spin-flip relaxation time of electrons in the quantum wells increases from 7 ps to 18 ps with increasing magnetic field up to 2 T due to the suppression of the exchange mechanism for the spin-flip relaxation of electrons interacting with Mn ions. In fields higher than 3 T, the electron spin-flip relaxation time turns to decrease caused by the LO phonon-related relaxation. The spin-flip time of holes is less than 200 fs due to the band-mixing effect in the valence bands.