K. Dziatkowski, et.al., Appl. Phys. Lett. 88, 142513

1
DMR 02-45227 Exchange bias in (Ga,Mn)As/MnO
Bilayers M. Dobrowolska, University of Notre Dame
Application spin valve and sensor applications
combined with GMR effect

• We found
• Unidirectional anisotropy in (Ga,Mn)As/MnO
  bilayers revealed by microwave FMR.
• An antiferromagnetic (AF) layer can effectively
  pin magnetic moments in (Ga,MN)As layer and the
  rotation (angular dependence) of magnetization
  during field reversal can be described by the
  single-domain model.
• Dependence of coercivity (HC) on temperature in
  (Ga,Mn)As is changed by the coupling to the AF
  layer.
• The exchange coupling is very robust with
  respect to temperature. Once established, it
  survives beyond the Nèel temperature of the AF
  layer (MnO).

Exchange bias (HEB) the shift of the M-H loop
Spin valve
Angular dependence
GMR
R (W)
B (T)
K. Dziatkowski, et.al., Appl. Phys. Lett. 88,
142513 (2006) Z. Ge, et al., (submitted to Phys.
Rev. B).
2
DMR 02-45227 Exchange bias in (Ga,Mn)As/MnO
Bilayers M. Dobrowolska, University of Notre Dame
Education Two grad students, Mr. (now Dr.) W.L.
Lim and Mr. Z. Ge and two undergraduate
students, Miss Carissa Reynolds and Miss Leanna
Steier, contributed to this work. Miss Reynolds
was an REU student from Wittenberg University,
and Miss Steier is a Notre Dame undergraduate
whom we employ part-time in our research group.
In addition, the Ph.D. research of Mr. (now Dr.)
Brian Kirby at the University of Missouri has
benefited directly from our work on exchange
bias. Dr. Kirby is now employed at NIST, where he
and his colleagues are continuing this work on
exchange bias.
Societal Impact Our group has been continually
active as a resource of materials for other
groups. We are currently interacting with at
least 30 other institutions by providing them
with magnetic semiconductor specimens for their
research. The understanding of these materials
and their heterostructures, as well as of devices
based upon them developed in our laboratory, is
thus automatically of benefit to our
collaborators (including graduate students in
their Ph.D. research), who depend not only on the
specimens that we provide, but on the
intellectual input from our group in the form of
characterization and general understanding of the
properties of these materials.