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

Paper MI+EL-MoM10
Epitaxial Growth and Annealing Studies of Single Crystal, Ferromagnetic Co@sub 2@MnGa of GaAs (100)

Monday, November 4, 2002, 11:20 am, Room C-205

Session: Spintronic Materials and Hybrid Devices
Presenter: D.M. Carr, University of Minnesota
Authors: D.M. Carr, University of Minnesota
S. McKernan, University of Minnesota
F.M. Abdulle, University of Minnesota
J.W. Dong, University of Minnesota
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
Spintronic devices that use electron spin in semiconductor devices are promising candidates for the next generation of electronic devices. Ferromagnetic metals with high spin polarization may be required for successful implementation of these devices. The Heusler alloys are a promising family of metals because the material properties such as lattice parameter, saturation magnetization, Curie temperature, and spin polarization can be altered by changing the elemental composition. In addition, their lattice parameters span most of the lattice parameters of the compound semiconductors. Films of the Heusler alloy Co@sub 2@MnGa have been epitaxially grown on GaAs (100) using molecular beam epitaxy. In situ reflection high-energy electron diffraction patterns and ex situ x-ray diffraction patterns of 300 Å thick films indicate single crystal growth with an out-of-plane lattice constant of 5.94 Å, which suggests tetragonally distorted growth since the bulk lattice parameter is 5.77 Å. Variable temperature vibrating sample magnetometry measurements show the Co@sub 2@MnGa films to be ferromagnetic with in-plane magnetization and a Curie temperature close to the bulk value of approximately 690 K. Ex situ annealing at different temperatures from 300 to 450 degrees C reveals an increase in the saturation magnetization and reduced coercivity for anneal times as short as 5 minutes at 425 degrees C. Annealed films exhibit a smaller out-of-plane lattice constant suggesting relaxation of the strained films. Cross sectional transmission electron microscopy studies will be used to characterize the level of interfacial reaction before and after annealing.