AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI+EL-WeM

Paper MI+EL-WeM2
Molecular Beam Epitaxial Growth of Ferromagnetic Ni@sub 2@MnGe on GaAs(001)

Wednesday, October 4, 2000, 8:40 am, Room 206

Session: Magnetic Semiconductors and Hybrid Structures I
Presenter: J. Lu, University of Minnesota
Authors: J. Lu, University of Minnesota
J.W. Dong, University of Minnesota
J.Q. Xie, University of Minnesota
D. Carr, University of Minnesota
V. Godlevsky, Rutgers University
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
A number of Heusler (L2@sub 1@) structures such as Ni@sub 2@MnX (X = Ga, In, Sn, Sb) are ferromagnetic shape memory alloys. The ferromagnetic Heusler alloys show promise as single crystal ferromagnetic spin polarized injecting contacts to semiconductors. In this work, epitaxial thin films of the Heusler alloy Ni@sub 2@MnGe have been for the first time grown on GaAs(001) substrate by molecular beam epitaxy (MBE). A two step growth procedure was used which included alternate layer epitaxy at 200°C of a thin Ni@sub 2@MnGe template layer followed by codeposition at 250°C. A (2x2) surface reconstruction was observed by in-situ reflection high energy electron diffraction. X-ray diffraction studies show that the Ni@sub 2@MnGe film is epitaxially grown on GaAs(001) with the crystallographic relationship: (001)@sub Ni2MnGe@//(001)@sub GaAs@, (110)@sub Ni2MnGe@//(110)@sub GaAs@ . X-ray diffraction was used to determine both the out of plane and in plane lattice parameters. These confirmed that the film had a tetragonal structure, with a = 5.65 ±0.02 Å c = 5.897 Å, and c axis perpendicular to film surface, suggesting pseudomorphic growth on the GaAs surface. The magnetic properties were measured using superconducting quantum interference device magnetometry (SQUID). The coercivity of the film is ~50 Oe, and the saturation magnetization Ms is ~ 200 emu/cm3. The Curie temperature was 330 ± 10 K. In this talk, the magnetic and structural properties of Ni@sub 2@MnGe/GaAs heterostructures as a result of growth procedures and composition will be discussed. Results from Rutherford backscattering and transmission electron microscopy studies will be correlated with the magnetic properties.