Highly ordered, half-metallic Co₂FeSi single crystals

A wide variety of properties such as half-metallicity is found among Heusler compounds. In order to separate intrinsic and extrinsic properties, high quality single crystals are required. Here, we report on differently grown crystals of the half-metallic ferromagnet Co2FeSi. All crystals show excellent ordering, resulting in outstanding electrical behavior with low residual resistivity and high residual-resistivity-ratio. All Co2FeSi crystals show a plateau in the resistivity below 50 K, which might point to half-metallic ferromagnetism. The cross-over from this unusual to more conventional transport (T2 dependence) around 50 K indicates the onset of spin flip scattering and thus is indispensable for understanding the strong temperature dependence of Co2FeSi tunneling magnetoresistance-devices