Influence of Ni2+ substitution by Co2+ on the morphology and magnetic properties of single domain CoαNi0.9-αZn0.1Fe2O4 nanoparticles

This study presents the effect of Ni2+ substitution by Co2+ on the structure, morphology and magnetic properties of CoαNi0.9-αZn0.1Fe2O4 nanoparticles calcined at different temperatures. Fourier-transform infrared spectroscopy revealed the presence of Fe-O, Co-O, Zn-O and Ni-O bonds in samples calcined at 200 °C, while the presence of the characteristic bonds of the SiO2 confirmed the embedding of CoαNi0.9-αZn0.1Fe2O4 at all calcination temperatures. Single phase poorly crystalline ferrite for samples calcined at 400 °C and ferrite accompanied by traces of Fe2SiO4 and SiO2 for samples calcined at high temperatures (800 and 1200 °C) were identified. The dependence of X-ray diffraction parameters on the Co2+ content of nanoparticles was also investigated. The increase in Co2+ content and calcination temperature led to crystallite growth from 4 to 43 nm, while the porosity decreased with the increase in Co2+ content and calcination temperature. The magnetic properties of the rectangular shape nanoparticles evolved proportionally with the particle size. The magnetization, coercivity and magnetocrystalline anisotropy increased with the increase in Co2+ content and calcination temperature. The shape of hysteresis loops indicated a superparamagnetic-like behavior of the nanoparticles calcined at 400 °C and a ferrimagnetic-like behavior at higher calcination temperatures (800 and 1200 °C). These features make the obtained nanoparticles attractive candidates for various technical applications.