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Ultrafast Enhancement of Ferromagnetism via Photoexcited Holes in GaMnAs

J. Wang, I. Cotoros, K. M. Dani, D. S. Chemla, X. Liu, J. K. Furdyna

cond-mat.stat-mecharXiv:cond-mat/0702439

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.

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