Molecular beam epitaxial growth and characterizations of Co–Mn–Ge Heusler thin films

We report on the growth of Co–Mn–Ge thin films on various substrates using low-temperature molecular beam epitaxy. The magnetic and transport properties of the films were investigated. The close-to-stoichiometric Co2MnGe film grown on GaAs(1 0 0) shows ferromagnetism and exhibits anomalous Hall effects at room temperature. The irreversibility of zero-field-cooled and field-cooled measurements suggests the formation of superparamagnetic clusters. On the other hand, the growth of Co2MnGe films on Ge buffer layer and Si(1 0 0) substrate is found to be unsuitable due to the degraded crystal qualities with weak magnetization signals.