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

Abstract

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 Ni 5Ge 3 and Co 5Ge 3 phases, both exhibiting high and low-temperature modifications. The purpose of this work was to synthesise by mechanical alloying the Ni 5Ge 3 and Co 5Ge 3 alloys and to study their structure and magnetic properties. Mechanical alloying processes performed for Ni 62Ge 38 and Co 62Ge 38 powder mixtures resulted in the formation of single phase Ni 5Ge 3 and Co 5Ge 3 nanocrystalline alloys after 20–50 h of processing. Ni 62Ge 38 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.