Condensed Matter Physics Seminar
Thursday, April 27, 2000, 2 p.m.
Plant Sciences Building, Room 1130
Magnetism in Semiconductors
(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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