Seminars Archive
Chris J. Palmstrøm
Abstract
Monday, June 5, 2000, 14:30
Seminar Room, ground floor, Building "T"
Sincrotrone Trieste, Basovizza
I.D. required for external visitors
Epitaxial Ferromagnetic Metal/GaInAs(001) Heterostructures.
Chris J. Palmstrm
(Department of Chemical Engineering and Materials Science,
University of Minnesota)
ABSTRACT
Ferromagnetic bcc FeXCo1-X and the Heusler alloy Ni2MnGa have been
successfully grown on GaAs(001) by molecular beam epitaxy. In-situ reflection
high energy diffraction and X-ray diffraction data show a cube-on-cube
epitaxy with FeXCo1X(001)||GaAs(001) and Ni2MnGa(001)||GaAs(001).
The Rutherford backscattering spectrometry channeling minimum yields of
c~3.5% and ~6% for FexCo1-x and Ni2MnGa, respectively, suggests high quality
single crystal films. In order to minimize interfacial reactions and to
control the initial nucleation during the ferromagnetic film growth, we
investigated the use of the epitaxial Sc1-xErXAs and NiGa as interlayers.
Reflection high energy electron diffraction, X-ray diffraction and cross-sectional
transmission electron microscopy indicate pseudomorphic Ni2MnGa single
crystal ferromagnetic film growth on both interlayer surfaces.
Vibrating sample magnetometry measurements show in-plane magnetization
for both FexCo1-x and Ni2MnGa. Square hysteresis loops were obtained with
the magnetic field applied along the easy axis of FexCo1-x. Magneto-Optic
Kerr Effect measurements were used to study the switching mechanism of
the magnetic moments. The magnetic properties of ferromagnet/semiconductor
heterostructures depended upon surface symmetry, crystal structure and
bonding of the interfacial layer. FexCo1-x films showed uniaxial anisotropy
when grown directly on GaAs (001) and four-fold anisotropy when grown on
a Sc1-xErxAs interlayer. Growth on vicinal substrates resulted in an additional
step structure symmetry-induced magnetic anisotropy, which increased with
angle of miscut. In this talk, the effects of the interlayer and vicinal
surfaces on the growth mode and magnetic properties of the ferromagnet/GaAs
heterostructures will be discussed.
