Magnetic properties of cobalt and cobalt-platinum alloy nanoparticles synthesized via microemulsion technique

Metallic cobalt and cobalt-platinum alloys of various nanometer sizes have been synthesized via the microemulsion technique and their magnetic properties have been characterized. Preparation of cobalt and cobalt-platinum alloy nanoparticles was achieved by reducing aqueous metallic salts confined in the polar regions of the reverse micelle of cetyltrimethyl bromide (CTAB) with sodium borohydride. These particles are further coated with gold by reducing aqueous gold salts with borohydride. The dc susceptibility data of 15 nm gold coated Co, CoPt and CoPt/sub 3/ particles exhibit a blocking temperature of 4 K, 80 K and 106 K and coercivity of 20 Oe, 300 Oe, and 415 Oe at 10 K, respectively. Annealing these samples at 400/spl deg/C further enhanced their magnetic properties. The two cobalt-platinum alloys have been synthesized and characterized by x-ray powder diffraction and transmission electron microscopy.