NiFeCuMo magnetic powders obtained by controlled mechanical alloying and annealing

Abstract

Magnetic nanocrystalline Ni–Fe–Cu–Mo powders are obtained by mechanical alloying in a planetary mill under Ar atmosphere and subsequent annealing. Several milling times have been used ranging from 2 to 24 h and a subsequent heat treatment has been performed in order to improve the solid-state reaction and to remove the internal stresses. The formation of the Ni–Fe–Cu–Mo alloy by mechanical alloying and annealing is evidenced by X-ray diffraction (XRD) and magnetic measurements. A typical grain size of 13±2 nm is obtained after 24 h of milling. A minimum in the spontaneous magnetisation vs. milling time shows that different processes are involved in the alloy formation. Thermomagnetic measurements are used to investigate the solid-state reaction process and to determine the Curie temperatures of the phases.