Microstructures and magnetic properties of Co–Cu nanoparticles prepared by arc-discharge

The microstructures and magnetic properties of nanoparticles of immiscible system Co–Cu prepared by arc-discharge have been studied. The particles are about 20–30 nm in diameter showing core/shell structure. The cores are Co–Cu solutions, and the shell is copper oxide. The loop shift in the hysteresis loop indicates the existence of the exchange bias between ferromagnetic and antiferromagnetic components at low temperatures. A block temperature about 180 K was observed for the Co–Cu nanoparticles. The thermal magnetization at low temperatures is not satisfied with Bloch's law.