Magnetic properties of epitaxial Co/sub 2/Cr/sub 1-x/Fe/sub x/Al full Heusler alloy thin films with the L2/sub 1/ structure

Ferromagnetic Co/sub 2/Cr/sub 1-x/Fe/sub x/Al thin films were deposited onto GaAs substrates by co-evaporation with molecular beam epitaxy. The film stoichiometry was obtained by in situ Auger electron spectroscopy analysis. Growth temperature was optimized to be 673 K by identifying superlattice peaks in X-ray diffraction patterns. Isotropic hysteresis with saturation magnetization of 100 emu/cm/sup 3/ was obtained for x=0. On the other hand, for 0.4 /spl les/ x /spl les/ 1, strong uniaxial anisotropy is observed with hard axes. Also by utilizing these films, magnetic tunnel junctions (GaAs/Co/sub 2/Cr/sub 1-x/Fe/sub x/Al/Al-O(or MgO)/Co/sub 0.9/Fe/sub 0.1//Ru/Co/sub 0.9/Fe/sub 0.1//Au) were fabricated. It showed a very small tunnel magnetoresistance ratio of less than 2% at 5 K. Spin polarization of the film was also estimated. The magnetic properties, especially magnetic moments near the interfaces can be improved by elimination of atomic disorder.