Fabrication and magnetic properties of Ni0.50.5Zn0.5Fe2O4 nanofibres by electrospinning

NiZn ferrite/polyvinylpyrrolidone composite fibres wereprepared by sol--gel assisted electrospinning.Ni_0.5Zn_0.5Fe₂O₄ nanofibres with a pure cubicspinel structure were obtained subsequently by calcination of thecomposite fibres at high temperatures. This paper investigates thethermal decomposition process, structures and morphologies of theelectrospun composite fibres and the calcinedNi_0.5Zn_0.5Fe₂O₄ nanofibres at differenttemperatures by thermo-gravimetric and differential thermalanalysis, x-ray diffraction, Fourier transform infrared spectroscopyand field emission scanning electron microscopy. The magneticbehaviour of the resultant nanofibres was studied by a vibratingsample magnetometer. It is found that the grain sizes of the nanofibresincrease significantly and the nanofibre morphology graduallytransforms from a porous structure to a necklace-like nanostructurewith the increase of calcination temperature. TheNi_0.5Zn_0.5Fe₂O₄ nanofibres obtained at 1000~℃for 2~h are characterized by a necklace-like morphology anddiameters of 100--200~nm. The saturation magnetization of the randomNi_0.5Zn_0.5Fe₂O₄ nanofibres increases from 46.5to 90.2~emu/g when the calcination temperature increases from 450 to1000~du. The coercivity reaches a maximum value of 11.0~kA/m at acalcination temperature of 600~du. Due to the shape anisotropy, thealigned Ni_0.5Zn_0.5Fe₂O₄ nanofibres exhibit anobvious magnetic anisotropy and the ease magnetizing direction isparallel to the nanofibre axis.