Structure and magnetic properties of mechanically alloyed Ni–Ge and Co–Ge alloys

Mechanically synthesised Ni and Co-base alloys exhibit interesting magnetic properties, suggesting their potential applications. The equilibrium Ni–Ge and Co–Ge phase diagrams reveal the existance of Ni5Ge3 and Co5Ge3 phases, both exhibiting high and low-temperature modifications. The purpose of this work was to synthesise by mechanical alloying the Ni5Ge3 and Co5Ge3 alloys and to study their structure and magnetic properties. Mechanical alloying processes performed for Ni62Ge38 and Co62Ge38 powder mixtures resulted in the formation of single phase Ni5Ge3 and Co5Ge3 nanocrystalline alloys after 20–50 h of processing. Ni62Ge38 alloy was ferromagnetically ordered for all milling times. In the case of Co–Ge alloy, magnetization measurements showed an evolution from ferromagnetic to paramagnetic ordering upon milling.