Ultrafast Enhancement of Ferromagnetism via Photoexcited Holes in GaMnAs
arXiv:cond-mat/0702439 · doi:10.1103/PhysRevLett.98.217401
Abstract
We report on the observation of ultrafast photo-enhanced ferromagnetism in GaMnAs. It is manifested as a transient magnetization increase on a 100-ps time scale, after an initial sub-ps demagnetization. The dynamic magnetization enhancement exhibits a maximum below the Curie temperature Tc and dominates the demagnetization component when approaching Tc. We attribute the observed ultrafast collective ordering to the p-d exchange interaction between photoexcited holes and Mn spins, leading to a correlation-induced peak around 20K and a transient increase in Tc.
4 pages