Structural and magnetic properties of nanograined Ni_0.7−yZn_0.3Ca_yFe₂O₄ spinels

Faculty of Science, Physics Department, Benha University, Benha 13518, Egypt

^a e-mail: mhmakled@fsc.bu.edu.eg

Received: 20 December 2013
Revised: 25 March 2014
Accepted: 15 April 2014
Published online: 10 June 2014

Abstract

Nanocrystalline Ni_0.7−yZn_0.3Ca_yFe₂O₄ (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 °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 °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.