Large Negative Magnetic Anisotropy of W/Fe/W (001) Epitaxial Trilayers

In this paper, we report that W/Fe/W (001) epitaxial trilayer films exhibit very large negative uniaxial magnetic anisotropy K_u. The magnitude of K_u increases with decreasing the Fe layer thickness and also exhibits significant temperature dependence varying from -2.1 × 10⁷ erg/cc at 300 K to -3.5 × 10⁷ erg/cc at 10 K for the Fe layer thickness of 0.5 nm. The large negative Ku is attributable to interface magnetic anisotropy in nature at the W/Fe interface and can be quantitatively reproduced by the firstprinciples calculation. The X-ray magnetic circular dichroism measurement at room temperature has revealed that the interfacial W atom is polarized in antiparallel with the magnetic moment of Fe. The induced magnetic moment of the interfacial W is almost the half of the values obtained by the first-principles calculation and the previous experiment at low temperature. This small induced W moment may be ascribed to the significant temperature dependence of the negative K_u.