AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI+TF-FrM

Paper MI+TF-FrM8
The Effects of Growth Temperature and Composition on the Magnetic Properties of Ni@sub 2@MnIn@sub x@ Epitaxial Films Grown on InAs (001)

Friday, November 8, 2002, 10:40 am, Room C-205

Session: Magnetic Thin Films and Surfaces
Presenter: J.Q. Xie, University of Minnesota
Authors: J.Q. Xie, University of Minnesota
J.W. Dong, University of Minnesota
J. Lu, University of Minnesota
X.Y. Dong, University of Minnesota
T.C. Shih, University of Minnesota
S. McKernan, University of Minnesota
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
Injecting spin-polarized electrons into a semiconductor from a ferromagnetic material is an emerging concept for novel electronic devices.@footnote 1@ InAs is the semiconductor of choice because of its high electron mobility and the ease to form an ohmic contact to it. Although no elemental ferromagnet is lattice matched to InAs, the lattice mismatch between the Heusler alloy Ni@sub 2@MnIn and InAs is only 0.2%. In bulk, Ni@sub 2@MnIn is reported to have a cubic (L2@sub 1@) crystal structure with a lattice constant a@sub 0@ = 6.069 Å and a Curie temperature ~ 314 K. Recent theoretical studies showed that the band structure alignment between Ni@sub 2@MnIn and InAs would enhance the injection of the minority spins, suggesting that Ni@sub 2@MnIn may be a good choice for spin injection as a ferromagnetic contact.@super 2@ In this presentation, we report on the epitaxial growth of Ni@sub 2@MnIn thin films on InAs (001) by molecular beam epitaxy. Determination of the crystal structure of Ni@sub 2@MnIn and effects of ordering and composition on magnetic properties of Ni@sub 2@MnIn are emphasized. Our transmission electron microscopy studies indicate the pseudomorphic growth of Ni@sub 2@MnIn in the B2 structure on InAs (001) with an orientation relationship of Ni@sub 2@MnIn(001) || InAs(001) and Ni@sub 2@MnIn<100> || InAs<100>. Magnetic measurements show that the Ni@sub 2@MnIn films have a Curie temperature ~ 170 K. The lower Curie temperature compared to the bulk value (~ 314 K) is believed to be due to the growth of Ni@sub 2@MnIn in the B2 structure. To improve the ordering of Ni@sub 2@MnIn thin films, effects of substrate temperature and interfacial layer are investigated. Composition was found to affect the Curie temperature dramatically. For Ni@sub 2@MnIn@sub 1.7@, a Curie temperature as high as ~ 290 K was obtained. @FootnoteText@ @footnote 1@S. A. Wolf et al., Science 294, 1488 (2001).@footnote 2@K. A. Kilian and R. H. Victora, J. Appl. Phys. 87, 7064 (2000).