Variation of Magnetism and Structure on Mechanically Alloyed Co?C Powder

Abstract

The variation of magnetic properties during mechanical alloying was studied in Co 100-x C x (x = 20, 50, 80) granular alloys. The structural evolution during mechanical alloying was complemented by X-ray diffractometry. With increasing processing time, X-ray diffraction peaks from Co and C phases became weaker and finally disappeared. The grain size was estimated to be about 20 nm from the broadening of the XRD peaks. The saturation of magnetization at a steady state value was another evidence for the formation of a saturated solid solution in the mechanically alloyed sample. During mechanical alloying, the exchange interaction among the Co atoms becomes weaker due to inter-diffusion of Co and C atoms. Both the Curie temperature, T C , and the spin wave stiffness constant, D, which were estimated from the temperature dependence of magnetization, decrease with increasing C content. This tendency indicates the isolation of Co clusters from the C matrix.