XRD analysis and magnetic properties of nanocrystalline Ni20Co80 alloys

• We use the Rietveld refinement for accurate analysis of the complex XRD patterns of the mechanically alloyed Ni20Co80 powders.
• Microstructural and structural parameters are correlated to the magnetic properties.
• Ni20Co80 powder mixture prepared by mechanical alloying process has not been studied yet at our knowledge.

The mechanical alloying process has been used to prepare nanocrystalline Ni20Co80 alloy from elemental Ni and Co powders in a planetary ball mill under argon atmosphere. Scanning electron microscopy, X-ray diffraction and magnetic measurements were carried out to investigate morphological, structural, microstructural and magnetic properties changes during the milling process. The interdiffusion of Co and Ni leads to a heterogeneous solid solution with Ni-rich and Co-rich environments after 12 h of milling. The end product is a mixture of a highly disordered structure, fcc-Ni(Co), fcc-Co(Ni) and hcp-Co(Ni) phases having different microstructural and structural parameters. The coercivity, Hc, decreases rapidly up to 3 h of milling to about 58.3 Oe and remains constant on further milling. The saturation magnetization, Ms, value of about 126 emu/g is obtained after 48 h of milling.