Synthesis of cobalt nanowires for advanced rare-earth free permanent magnets

Abstract

This work aims to search an optimized condition for synthesis of cobalt nanowires by chemical methods, i. e chemical reduction method and polyol method. It is found that the polyol method can prepare nanorods or nanowires of cobalt when used the optimized solvent and starting materials whereas the reduction method generates cobalt nanoparticles with irregular in size and shape. The obtained cobalt nanostructures possess a hexagonal crystalline structure in the case of rods and possess a tetragonal structure in the case of spherical particles. According to magnetic properties of the particles, the hexagonal cobalt nanorods provide high coercivities (more than 2 kOe) in contrast to the spherical particles that give low coercivities (below 500 Oe). This can be attributed to the difference in magnetic shape anisotropy.