L2_1構造を有するCo_2Cr_<1-x>Fe_xAl薄膜の結晶構造と磁気特性(薄膜)

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We successfully grew Co_2Cr_<1-x>Fe_xAl full Heusler films (0 ≤ x ≤ 1) with the L2_1 structure onto GaAs(001) substrates by achieving stoichiometry in an ultrahigh-vacuum molecular beam epitaxy chamber. The films develop epitaxial crystallinity with the relationship of Co_2Cr_<1-x>Fe_xAl(001)<110>ll GaAs(001)<110>, which induces very strong uniaxial magnetocrystalline anisotropy, except for x = 0. For x = 1, in particular, the film is almost a single phase and its magnetic moment per formula unit exhibits Slater-Pauling behavior. Films of this type were used to fabricate magnetic tunnel junctions with 8.8% and 4.9% tunnel magnetoresistance (TMR) ratios at room temperature for x = 1 with an Al-O tunnel barrier and x = 0.6 with a MgO barrier, respectively. The TMR ratio can be further enhanced by both realizing an L2_1 single phase and eliminating lattice distortion.
社団法人日本磁気学会の論文
2005-02-01