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

Paper MI+EL-WeM1
Characterizations of MBE Grown Single Crystal Ferromagnetic Ni@sub 2@MnGa Thin Films on (001) Ga@sub 1-x@In@sub x@As

Wednesday, October 4, 2000, 8:20 am, Room 206

Session: Magnetic Semiconductors and Hybrid Structures I
Presenter: J.W. Dong, University of Minnesota
Authors: J.W. Dong, University of Minnesota
J.Q. Xie, University of Minnesota
L.C. Chen, University of Minnesota
M.T. Figus, University of Minnesota
S. McKernan, University of Minnesota
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
Minimization of spin flip scattering at the interface of ferromagnetic metal/semiconductor is expected with the use of high quality epitaxially grown ferromagnetic metal/semiconductor heterostructures with minimal interfacial reactions. The Heusler alloy Ni@sub 2@MnGa is ferromagnetic at room temperature and has the cubic L2@sub 1@ Heusler structure with lattice parameter 3% larger than that of GaAs. We have demonstrated MBE growth of 900 Å-thick single crystal Ni@sub 2@MnGa on (001) GaAs with a 6 monolayer-thick Sc@sub 0.3@Er@sub 0.7@As interlayer, which acts as a template layer and a diffusion barrier. Reflection high energy electron diffraction, X-ray diffraction, and transmission electron microscopy (TEM) studies confirm the single crystal structure of the Ni@sub 2@MnGa films and indicate that the growth is pseudomorphic on GaAs substrates. These results suggest an epitaxially stabilized tetragonal phase of Ni@sub 2@MnGa with a = b = 5.65 Å, c = 6.12 Å, which has not been found in the bulk. High resolution cross section TEM image shows that the interface between Ni@sub 2@MnGa films and the Sc@sub 0.3@Er@sub 0.7@As interlayer is atomically abrupt. The Rutherford backscattering channeling minimum yield of 6.5% further confirms the high quality of the Ni2MnGa films. At room temperature, magnetic measurements using a vibrating sample magnetometer show that the films are ferromagnetic with a coercivity of ~50 Oe, a saturation magnetization of ~250 emu/cm@super 3@, and a weak in-plane magnetic anisotropy. Using a superconducting quantum interference device magnetometer, the Curie temperature of the films is found to be ~340 K. Our results indicate that Ni@sub 2@MnGa/GaAs can form high quality ferromagnetic metal/semiconductor heterostructures that might be used for spin injection measurements. In this talk, the effect of interlayer and strain on the structural and magnetic properties of Ni@sub 2@MnGa on Ga@sub 1-x@In@sub x@As substrates will be discussed.