Effects of postdeposition heat treatment on the structural and magnetic properties of CoFe2O4 nanoparticles produced by pulsed laser deposition

In this work, we investigated the effects of postdeposition heat treatment on structural and magnetic properties of CoFe2O4 nanoparticles produced by pulsed laser deposition. Structural analysis by X-ray diffraction, transmission electron microscopy (TEM) and Mössbauer spectroscopy indicate the formation of a single phase cobalt ferrite nanoparticles with the size ranging from 4.3 to 33.3 nm depending on the annealing temperature. The magnetic properties of the samples were investigated in a wide temperature range (50-400 K). Noticeable effects of the cubic magnetocrystalline anisotropy on the magnetization process of nanoparticles were observed for samples annealed at 450 °C and 600 °C, while for samples as-deposited and annealed at 300 °C the magnetization properties were dominated by a uniaxial effective anisotropy. ΔM technique was used to investigate the magnetic interaction among the nanoparticles. Only demagnetizing interactions were observed for the sample annealed up to 300 °C, while for the samples treated at 450 °C and 600 °C, both magnetizing and demagnetizing interactions were observed. The results are discussed considering the evolution of the nanoparticles' nanostructure with anneals and its effects on the magnetic properties. Fil: Fabris, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidade Federal Fluminense; Brasil Fil: Xing, Y.T.. Universidade Federal Fluminense; Brasil Fil: Franceschini, D.F.. Universidade Federal Fluminense; Brasil Fil: Sanchez, D.R.. Universidade Federal Fluminense; Brasil Fil: Alzamora, M.. Universidade Federal do Rio de Janeiro; Brasil Fil: Nunes, W.C.. Universidade Federal Fluminense; Brasil