Evolution of magnetic properties of crystalline cobalt-iron boride nanoparticles via optimization of synthesis conditions using hydrous metal chlorides

Abstract Chemical synthesis of crystalline and nanoscale cobalt-iron metal boride powders was studied using hydrous metal chlorides and NaBH4. The effects of precursor concentration and optimized synthesis conditions on the phase formation, microstructure, and magnetic properties were investigated. After applying a reaction of CoCl2·6H2O-FeCl3·6H2O-NaBH4 at 850 °C, (CoFe)B2, (CoFe)B, Co2B, Fe3B, and Fe0.71Co0.29 boride phases were obtained from different synthesis conditions applied under autogenic pressure or Ar flow atmosphere. Oxychloride impurities were the reason for the reduced magnetization values. The highest saturation magnetization of 183 emu/g belongs to obtained nanoparticles containing (CoFe)B2 and (CoFe)B pure phases. High temperature magnetic measurements marked synthesized powders as soft magnetic materials up to 795 K while no Tc was reached for the obtained phases.