Structural and magnetic characterization of Co-Cu nanoparticles prepared by arc-discharge

¹ Shenyang National Laboratory for Materials Science, Institute of Metal Research and International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, P.R. China
² Institute of Experimental Physics, Slovak Academy of Sciences, 04353 Kosice, Slovakia
³ Laboratory of Ultrafine Particles, Shenyang Polytechnic University, Shenyang 110023, P.R. China

Corresponding author: cyyou75@hotmail.com

Received: 18 November 2003
Revised: 17 March 2004
Accepted: 23 March 2004
Published online: 25 August 2004

Abstract

The structure and magnetic properties of the nanoparticles of immiscible system Co₂₀Cu₈₀ prepared by means of arc-discharge, have been studied in detail. The diameters of the particles are about 20 ~ 30 nm and a core/shell structure forms. The cores are Co-Cu solutions, which show some small Co precipitates, encapsulated with a shell of cupper oxide or cobalt oxide as observed by means of high-resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDS). 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 has been observed for as-deposited nanoparticles. For the annealed nanoparticles, the thermal magnetization at low temperatures is satisfied with Bloch's law.