Composition dependence of magnetic anisotropy and quadratic magnetooptical effect in epitaxial films of the Heusler alloy Co2MnGe

Magnetic anisotropy and magnetooptic Kerr effect for epitaxial films of Co_xMn_yGe_1−x−y grown on Ge (1 1 1) substrates have been studied systematically in the compositional vicinity of the Heusler alloy Co₂MnGe. A large quadratic magnetooptic Kerr effect has been observed within a narrow region of composition centered around the Co to Mn atomic ratio of 2. The effect has been used to probe and quantify the magnetic anisotropy of the system, which is shown to have a strong sixfold in-plane component accompanied by a weak uniaxial component at room temperature. These properties are shown to depend sensitively on atomic ratio between Co and Mn, indicating the presence of an intrinsic composition-driven phenomenon.