Magnetic and structural properties of Co50Ni50 powder mixtures


N. Loudjani1,* and N. Bensebaa2


1Laboratory of Magnetism and Spectroscopy of Solids (LM2S), Department of Physics, Faculty of

Science, University Badji Mokhtar of Annaba, Annaba, Algeria

2Algeria Laboratory of Radiation, University of Annaba, Annaba, Algeria

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In the present work, morphological, structural, thermal and magnetic properties of nanocrystalline Co50Ni50  alloys prepared by high energy planetary ball milling have been studied  by  means  of  scanning  electron  microscopy,  X-ray  diffraction,  and  differential scanning calorimetry. The coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. Morphological observations indicated a narrow distribution in the particle and homogeneous shape form with mean  average  particle  size  around  130 µm2.  The  results  show  that  an  allotropic  Co transformation hcp   fcc occurs within the three first hours of milling and contrary to what expected, the Rietveld refinement method reveals the formation of two fcc solid solutions (SS): fcc Co(Ni) and Ni(Co) beside a small amount of the undissolved hcp Co. Thermal

measurement, as a function of milling time was carried out to confirm the existence of the hcp phase and to estimate its amount. Magnetic measurement indicated  that the 48 h milled powders with a steady state particles size have the highest saturation (105.3 emu/g) and the lowest coercivity (34.5 Oe).


Keywords:   nanocrystalline   materials,   mechanical   alloying,   Co50Ni50     alloy,   microstructure, calorimetry, magnetic measurement