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 Ga1-xMnxAs 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 Ga1-xMnxAs is itself strongly spin polarized.  The evolution of this two-component ferromagnetism with increasing hole concentration distinguishes Ga1-xMnxAs from a traditional RKKY system.

Host:  Igor Zutic

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