Perpendicular Magnetic Anisotropy of Co2FexMn1−xSi Heusler Alloy Ultra-Thin Films

Film thickness, composition, and buffer layer dependences of perpendicular magnetic anisotropy (PMA) were investigated for ultrathin Co₂Fe_xMn_1-xSi Heusler alloy films. The perpendicular magnetization was achieved when the thickness of the Co₂MnSi on the Pd buffer layer was 0.6 and 0.8 nm. For Co₂FeSi, only a 0.6 nm thick film exhibited perpendicular magnetization. Effective uniaxial magnetic anisotropy energy (Keffu ) was 1-2 × 106 erg/cm³. From the buffer layer dependence, it was revealed that perpendicular magnetization of Co₂FeSi films was not achieved for a MgO or Cr buffer layer. These results imply that contributions from the Pd/Heusler alloy interface plays an important role in the PMA of ultrathin Co₂Fe_xMn_1-xSi Heusler alloy films.