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 ^{111}In(^{111}Cd) tracers with the perturbed angular correlations technique. Small cobalt oxide nanoparticles with the characteristic size of 6.5 nm have been prepared by the wet chemical route that turned out to be essential to incorporate radioactivity tracers during nucleation and growth of the particles. Nanocrystalline samples with 22.1 nm size were obtained by thermal treatments under low pressure of helium at 670 K. The hyperfine data were correlated with X-ray diffraction, ZFC–FC magnetic measurements, and transmission electron microscopy 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.
Highlights
We report a comprehensive investigation on the magnetic, structural, and electric properties of Cobalt monoxide (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 technique
S1 was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetizaton measurements just after synthesis, whereas S2 was characterized by the same techniques after annealing, which was carried out during perturbed angular correlation (PAC) measurements at temperatures in the range from 295 K to 670 K
Other interesting characteristic on zero field cooling and field cooling (ZFC–field cooling (FC)) curves is the behavior at low temperature; our results show a pronounced increase of magnetization, which can be called paramagnetic tails
Summary
We 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 technique. 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. Due to their great potential for application in new technological devices, magnetic nanoparticles (NPs) have captured the attention of researchers in several areas of scientific knowledge, and are being studied with increasing interest, promoting mainly the investigation of new synthesis routes and characterization methodology with the purpose to improve their p erformance[1,2,3]. Considering that the magnetization in a magnetic nanoparticle is measured with a measurement time τm , if in one experiment τm ≫ τN , the nanoparticle magnetization will flip several times during the measurement and the measured
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