Crystalline and magnetic properties of CoO nanoparticles locally investigated by using radioactive indium tracer

Abstract

We herein report a comprehensive investigation on the magnetic, structural, and electric properties of CoO nanoparticles with different sizes by local inspection through hyperfine interactions measured in a wide range of temperatures (10-670 K) by using radioactive 111In( 111Cd) tracers with the perturbed angular correlations (PAC) technique. Small cobalt oxide nanoparticles with 6.5 nm have been prepared by the wet chemical route, which has shown essential to incorporate radioactivity tracers during nucleation and grown syntheses. Nanocrystalline samples with 22 nm size were obtained by thermal treatments under low pressure of helium at 670 K. The hyperfine data were correlated with X-ray diffraction (XRD), ZFC-FC magnetic measurements and transmission electron microscopy (TEM) to describe the structure, magnetic properties, size, and shape of samples. An analysis of the temperature evolution of hyperfine parameters revealed that the structural distortion and the magnetic disorder in the core and on the surface layer play an important role in the magnetic behavior of CoO nanoparticles.