Synthesis of nanocrystalline Co–Ni alloys by precursor approach and studies on their magnetic properties

Nanocrystalline Co–Ni alloys with different compositions were prepared by polyol reduction of mixed cobalt nickel hydroxides. The precursors (mixed cobalt nickel hydroxides) were prepared by co-precipitation. Powder X-ray diffraction analysis indicated the formation of fcc phase in the alloys and their crystallite size in the range 17–25 nm. Scanning electron microscopy and transmission electron microscopy studies revealed the morphology of the particles as being close to spherical, and the energy dispersive X-ray analysis showed the stoichiometry of the alloys. The magnetization as a function of field and temperature of the alloys, measured using a superconducting quantum interference device, showed superparamagnetic behavior with negligible coercivity and remanence values.

► Synthesis of nanocrystalline Co–Ni alloys by an easy polyol reduction method. ► Composition and magnetic properties of the alloys may be tuned easily. ► Synthesis method has the potential to be extended to other bi- and tri-metallic nanocrystalline alloys.