Structural and magnetic properties of nanograined Ni0.7-yZn0.3CayFe2O4 spinels

Nanocrystalline Ni0.7-yZn0.3CayFe2O4 (0.0 <= y <= 0.7) has been obtained by soft coprecipitation method at different calcination temperatures. The influence of Ca2+ content and heat treatment on microstructure and magnetic properties are investigated using X-ray diffraction (XRD), thermal analysis, scanning electron microscope (SEM), atomic force microscope (AFM) and infrared (IR) spectroscopy. XRD analysis reveals single phase of spinel structure in ferrite with y = 0.2. An endothermic peak in DSC curve is appeared around 700 degrees C for all compositions due to collapse of the defective surface layer covers the grains. IR spectra for precursors or calcined ferrites shows the existence of bands characteristic for cubic spinel phase. The higher values for specific saturation magnetization (M-s) was obtained for ferrites calcined at 600 degrees C. Paramagnetic ordered particles was dominated when Ca2+ content increases more than 0.3. On the other hand, the coercivity of the present ferrites is strongly depends on Ca2+ content than calcination temperature.