AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI+EL-MoM

Paper MI+EL-MoM11
Growth Temperature Controlled Magnetism in Molecular Beam Epitaxially Grown Ni@sub 2@MnAl Heusler Alloys

Monday, November 4, 2002, 11:40 am, Room C-205

Session: Spintronic Materials and Hybrid Devices
Presenter: X.Y. Dong, University of Minnesota
Authors: X.Y. Dong, University of Minnesota
J.Q. Xie, University of Minnesota
J.W. Dong, University of Minnesota
T.C. Shih, University of Minnesota
S. McKernan, University of Minnesota
C. Leighton, University of Minnesota
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
The Heusler alloy Ni@sub 2@MnAl is thought to be either antiferromagnetic or ferromagnetic depending on its crystal structure, B2 (disordered Mn-Al sublattice) or L2@sub 1@.@super 1@ This suggests that a ferromagnet/antiferromagnet interface should be possible to be formed with Ni@sub 2@MnAl by controlling its crystal structure. Single crystal Ni@sub 2@MnAl thin films have been grown by MBE on GaAs (001) using Sc@sub 0.3@Er@sub 0.7@As interlayers. The effects of growth temperature on its structural and magnetic properties were studied. For all the films grown at different temperatures, streaky RHEED patterns were observed during the growth. The Ni@sub 2@MnAl / Sc@sub 0.3@Er@sub 0.7@As / GaAs (001) films were single crystals with cube on cube epitaxial relationship. The Rutherford backscattering spectrometry channeling minimum yield, @chi@@sub min@, of ~ 5 %, confirms a relatively good quality crystal. XRD and TEM show that the Ni@sub 2@MnAl films have a tetragonally distorted structure with its c axis oriented along the growth direction. Higher growth temperature tends to result in ferromagnetic films suggesting a more L2@sub 1@-like structure, while lower temperature growth gives rise to non-ferromagnetic behavior, suggesting a more B2-like structure. For the ferromagnetic Ni@sub 2@MnAl film, the Curie temperature was determined to be approximately 220K. The exchange bias effect was observed for Co (70Å) / Ni@sub 2@MnAl (360Å, B2-like structure) bilayers, suggesting that the low temperature grown Ni@sub 2@MnAl is antiferromagnetically ordered. Therefore the self exchange biased Ni@sub 2@MnAl bilayers can be expected to be grown by varying the temperature during the growth. In this presentation, the effect of growth temperature on the structural and magnetic properties will be emphasized as well as the approaches of making self exchange biased structures will be reported. @FootnoteText@ @footnote 1@ F. Gejima, Y. Sutou, R. Kainuma, and K. Ishida, Metal. Mater. Trans. A 30A, 2721 (1999).