Abstract
The ultrafast demagnetization of Co2FeAl thin film grown on n-GaAs by molecular beam epitaxy was investigated with the time-resolved magneto-optical Kerr technique, by varying temperature, pump wavelength and fluence. A faster demagnetization with stronger magnetization quenching was observed at the on-resonant excitation of GaAs band-edge at 10 K. In addition, the pump fluence dependent ultrafast demagnetization at 10 K exhibits different behavior from that of the room temperature case. The enhanced spin angular momentum dissipation induced by the spin pumping effect was suggested to contribute to the ultrafast demagnetization for Co2FeAl thin film epitaxied on GaAs especially at low temperature, in addition to the local spin-flip scattering. Our results provide experimental proof for the ultrafast demagnetization facilitated by the spin pumping effect, which is of great importance for understanding the ultrafast spin angular momentum dissipation in ferromagnetic/semiconductor heterojunctions.
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