Condensed Matter Physics Seminar

Thursday, April 27, 2000, 2 p.m.
Plant Sciences Building, Room 1130

Magnetism in Semiconductors

Paul Crowell

(School of Physics and Astronomy, University of Minnesota)

Abstract: For years most of the experimental effort in magnetic semiconductors has focused on the II-VI family of materials, in which substitution of a magnetic ion for the cation leads to the enhancement of the ordinary Zeeman interaction and a correspondingly large carrier spin polarization. This leads to a variety of interesting phenomena, including magnetic polarons, but not ferromagnetism. The recently discovered III-V ferromagnetic semiconductor Ga_1-xMn_xAs is a very different system, in which the Mn ion introduces a hole as well as a magnetic moment. The ferromagnetism is a robust phenomenon, with Curie temperatures as high as 100 K for Mn concentrations of 4%. Magneto-circular dichroism measurements indicate that the hole population in Ga_1-xMn_xAs is itself strongly spin polarized. The evolution of this two-component ferromagnetism with increasing hole concentration distinguishes Ga_1-xMn_xAs from a traditional RKKY system.

Host: Igor Zutic

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