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

Zhiqing Yang 1Caiyin You 2

1. University of Antwerp, Department of Physics, Antwerp, Belgium
2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

Abstract

The investigations on ultra-fine particles of the immiscible system, such as Co-Cu and Co-Ag, are very challenging due to potential higher magnetoresistance and fundamental understanding how bulk properties transform to atomic ones. In the present study, immiscible Cu-Co nanoparticle was successfully prepared by arc-discharge technique in an atmosphere of a mixture of H2 (30%) and He (70%). Microstructures and magnetic propertied were investigated by using advanced transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID). Most of the particles have sizes of 20~30 nm in diameters. High-resolution TEM observations reveal core-shell microstructures with coherent interfaces. Composition of the nano-particles was analyzed by nano-probe energy dispersive X-ray (EDX) analysis, revealing microstructure of cores of Cu-Co solutions covered by oxide shells. Co particles were occasionally observed. The magnetic properties have been analyzed by temperature dependence of magnetization, zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements. 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.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium B, by Zhiqing Yang
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-16 12:03
Revised:   2009-06-07 00:44
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