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Phys. Rev. B 77, 235308 (2008) [6 pages]

Femtosecond demagnetization and hot-hole relaxation in ferromagnetic Ga1−xMnxAs

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J. Wang1,*, Ł. Cywiński2,†, C. Sun1, J. Kono1,‡, H. Munekata3, and L. J. Sham2
1Electrical and Computer Engineering Department, Rice University, Houston, Texas 77005, USA
2Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
3Imaging Science and Engineering Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan

Received 2 April 2008; published 12 June 2008

We have studied ultrafast photoinduced demagnetization in GaMnAs via two-color time-resolved magneto-optical Kerr spectroscopy. Below band gap midinfrared pump pulses strongly excite the valence band, while near-infrared probe pulses reveal subpicosecond demagnetization that is followed by an ultrafast (∼1 ps) partial recovery of the Kerr signal. Through comparison with InMnAs, we attribute the signal recovery to an ultrafast energy relaxation of holes. We propose that the dynamical polarization of holes through p-d scattering is the source of the observed probe signal. These results support the physical picture of femtosecond demagnetization proposed earlier for InMnAs, identifying the critical roles of both energy and spin relaxation of hot holes.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.77.235308
DOI:
10.1103/PhysRevB.77.235308
PACS:
78.20.Jq, 42.50.Md, 78.30.Fs

*Present address: Lawrence Berkeley National Laboratory, Berkeley, CA, USA; jwang5@lbl.gov

†Present address: Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, MD, USA; lcyw@umd.edu

‡Corresponding author; kono@rice.edu

 
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