Related magnetic properties of CoFe2O4 cobalt ferrite particles synthesised by the polyol method with NaBH4 and heat treatment: new micro and nanoscale structures

Abstract

In this contribution, hierarchical CoFe₂O₄ particles are successfully prepared via a modified polyol elaboration method with NaBH₄ and a proposed heat treatment process. Here, new as-prepared CoFe₂O₄ particles with sizes in the range of 5 μm show highly uniform characteristics in their size, shape and cubic spinel crystal structure according to X-ray diffraction (XRD), whole pattern fitting and Rietveld refinement, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). We discovered that the CoFe₂O₄ microparticles prepared in the certain size range of 5 μm show exciting configurations of grain and grain boundaries under particle heat treatment at the high temperature 900 °C. Finally, CoFe₂O₄ ferrite particles with various well-defined micro and nanoscale structures were produced after appropriate heat treatment processes under high temperature, and which have a high coercive field, H_C, around 416–888 Oe, and the highest saturation magnetization, M_S, of about 74–91 emu g⁻¹ at room temperature (RT) for all of the as-prepared samples measured using a vibrating sample magnetometer (VSM). Here, the magnetic behavior has shown persuasive evidence that the desirable ferrimagnetic properties of CoFe₂O₄ oxides do not only depend on their size but also on the spinel structure of the CoFe₂O₄ oxides as well. Finally, the as-prepared CoFe₂O₄ particles with the formula CoO·Fe₂O₃ were regarded as the best inverse ferrimagnetic materials with magnetic parameters of H_C at 896 Oe, M_R/M_S squareness around 0.420, and M_S around 92 emu g⁻¹ at 20 kOe for the downward part of the hysteresis loop.