Fine metal particles having super high coercivity

Fine iron-cobalt particles with coercivities as high as 2200 Oe have been obtained. The particles were precipitated from an aqueous solution using sodium borohydride. The coercivity was studied as a function of composition with the maximum coercivity found at 65:35 (Fe:Co ratio). The coercivity was found to arise from two effects. The first is shape anisotropy due to the chain of spheres structure of the particles. The second is a high magnetic surface anisotropy. No evidence of a contribution from magnetocrystalline anisotropy was found.