Synthesis and temperature dependent magnetic properties of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrites

Ni0.5Zn0.5Fe2O4 nanoparticles were successfully synthesized by modified citrate gel method. X-ray diffraction (XRD) analysis confirmed the development of single-phase cubic spinel structure with Fd (3) over barm space group. The cation distribution was estimated by Rietveld refinement of XRD pattern and found that the prepared sample has a mixed spinel structure. The high field regions of magnetic hysteresis loops were modeled using the Law of Approach to Saturation to determine the saturation magnetization (M-s) and magnetic anisotropy constant (K-1) for the prepared nanoparticles. It is found that the values of M-s and K-1 increases significantly with decreasing temperature. However, temperature dependence of saturation magnetization (M-s) and coercivity (H-c) were found to have considerable deviations from the Bloch's and Kneller's laws, respectively. This behavior is elucidated in terms of finite size effects, disordered surface spins and interparticle interactions in the prepared nanoparticles. Furthermore, the effects of interparticle interactions were investigated by using Vogel- Fulcher law for frequency dependent AC susceptibility measurements.