Regensburg 2000 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 43: III-V Halbleiter
HL 43.2: Vortrag
Freitag, 31. März 2000, 10:45–11:00, H13
Magnetic Circular Dichroism Studies of Carrier Induced Ferromagnetism in GaMnAs — •B. Beschoten1, P.A. Crowell1, I. Malajovich1, D.D. Awschalom1, F. Matsukura2, A. Shen2, and H. Ohno2 — 1Department of Physics, University of California, Santa Barbara, CA 93106 — 2Laboratory for Electronic Intelligent Systems, Research Institute of Electronic Communication, Tohoku University, Sendai 980-77, Japan
Magnetic circular dichroism (MCD) is used to investigate the evolution of ferromagnetism in the p-type magnetic semiconductor (Ga1−xMnx)As. We observe an unusual MCD signal comprising two spectroscopically distinct contributions: a broad spectrum that scales with the thermodynamic magnetization of the sample and a narrower peak (∼150meV FWHM) which appears only in the ferromagnetic phase [1]. This peak is attributed to the spontaneous spin splitting of the hole density of states. Its sign indicates that the exchange between holes and the local magnetic moments is antiferromagnetic. The distinct temperature and magnetic field dependence of both contributions for insulating and metallic samples along with the large spin polarization that can be inferred from transport measurements suggest that the holes in GaMnAs do not simply play the role of a Fermi sea mediating a RKKY like exchange interaction. BB was supported by the AvH, V-3-FLF-1052866. Work supported by the AFOSR F46920-99-1-0033, the ONR N00014-99-1-0077, the NSF DMR-9701072, and by the JSPS and the Spin-Controlled Semiconductor Nanostructure program from the Ministry of Education, Japan. [1] B. Beschoten et al., Phys. Rev. Lett.83, 3073 (1999).