We present a dynamical model that successfully explains the observed time evolution of the magnetization in diluted magnetic semiconductor quantum wells after weak laser excitation. Based on the pseudo-fermion formalism and a second order many-particle expansion of the exact p-d exchange interaction, our approach goes beyond the usual mean-field approximation. It includes both the sub-picosecond demagnetization dynamics and the slower relaxation processes which restore the initial ferromagnetic order in a nanosecond time scale. In agreement with experimental results, our numerical simulations show that, depending on the value of the initial lattice temperature, a subsequent enhancement of the total magnetization may be observed within a time scale of few hundreds of picoseconds.
@article{arxiv.0901.4541,
title = {Ultrafast Magnetization Dynamics in Diluted Magnetic Semiconductors},
author = {O. Morandi and P. -A. Hervieux and G. Manfredi},
journal= {arXiv preprint arXiv:0901.4541},
year = {2015}
}