Comparing Different Approaches to Form Cobalt Oxide Layer on CoPt Nanoparticles

Abstract

We have studied the effect of preparation methods, under argon gas and in the air environment, on the cobalt oxide formation of CoPt nanoparticles by the polyol process. The formation of cobalt oxide for both samples was investigated by the x-ray diffraction (XRD) method and cobalt oxide peaks are observed in the air prepared sample. Rietveld refinement analyses revealed that all samples exhibit a chemically distorted cubic crystal structure. The average particle size was determined <8 nm by scanning electron microscopy (SEM) and energydispersive x-ray spectroscopy (EDS) was revealed the chemical compositions with possible oxygen formation in the structure. The blocking temperature is reduced to 28 K in the air prepared sample due to cobalt oxide formation. The hysteresis gap disappeared above the blocking temperature and no saturation is observed up to ±5 T external field due to the system switching