Synthesis of nanocrystalline nickel-iron alloys-A novel chemical reduction method

Abstract

Ultra fine magnetic particles of NixFe100-x alloys were synthesized by a novel chemical reduction of the precursor salts by an alkali earth metal (Al) in an aqueous medium. In this method we successfully prepared alloy nanocrystalline powders without any bimetallic phases. The alloys were formed with Fe at% in two distinct bands 18–30 and 60–90 irrespective of the concentration ratios of Ni and Fe sources. The NixFe100-x alloy composition showed a transformation from fcc to bcc structure .The Ni rich alloys namely NixFe100-x (x = 90 to75) which correspond to 18–30 band Fe at%.composition were formed in fcc (or simple cubic) phase, whereas the Fe rich alloys (x = 80) which correspond to 66–90 band Fe at%.composition were formed in bcc phase. The observed grain sizes for Ni rich (i.e., 18–30 Fe at.%) alloys lie in the range of 6–9 nm whereas for the Fe rich alloys grains are in the 20–27 nm range. Magnetization measurements shows that all the alloys exhibit ferromagnetic behaviour and the saturation magnetization values increase linearly with iron content. Vibrating sample magnetometer measurements shows that all samples exhibit ferromagnetic behaviour with increasing saturation magnetization as a function of iron content. SEM studies shows that the particles were found be large and agglomerated.