Epitaxy of half-metallic Heusler alloy Co2MnSi on Ge(111) substrate via a graphene interlayer with L21-ordered Co2MnSi

Cubic half-metallic Heusler alloy Co2MnSi (CMS) thin films were epitaxially grown on Ge(111) substrates via a hexagonal graphene interlayer through the combined use of magnetron sputtering for CMS and mechanical exfoliation for graphene. Despite the graphene interlayer being inserted between the CMS film and the Ge(111) substrate, CMS films were still grown epitaxially on Ge(111) substrates with extremely smooth and abrupt interfaces. Furthermore, 111 peaks of CMS were observed by x-ray diffraction measurement, indicating the L21 order for CMS thin films. The saturation magnetization (Ms) of CMS films annealed at 450 °C was 891 emu/cm3 at 10 K, which is correspondence to 87% of the theoretically predicted saturation magnetization value for half-metallic CMS.