Ultrafast enhancement of ferromagnetism via photoexcited holes in GaMnAs.
We report on the observation of ultrafast photoenhanced ferromagnetism in GaMnAs. It is manifested as a transient magnetization increase on a 100 ps time scale, after an initial subpicosecond demagnetization. The dynamic magnetization enhancement exhibits a maximum below the Curie temperature T(c) and dominates the demagnetization component when approaching T(c). 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 20 K and a transient increase in T(c).
Materials Sciences Division, Lawrence Berkeley National Laboratory and Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
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Wang
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Cotoros
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Dani
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Liu
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Furdyna
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Chemla