Synthesis of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite and study of its magnetic behavior at different temperatures

Ni0.5Zn0.5Fe2O4 ferrite nanocrystals with average diameter in the range of 1–2 nm have been synthesized by reverse microemulsion. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) are used to characterize the structural, morphological and magnetic properties. X-ray analysis showed that the nanocrystals possess cubic spinel structure. The absence of hysteresis, negligible remanence and coercivity at 300 K indicate the superparamagnetic character and single domain in the nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite materials. The nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite were annealed at 600 °C. As a result of heat treatment the average particle size increases from 2 nm to 5 nm and the corresponding magnetization values have increased to 21.69 emu/g at 300 K. However, at low temperature of 100 K, the annealed samples show hysteresis loop which is the characteristic of a superparamagnetic to ferromagnetic transition. In addition, a comparative study of the magnetic properties of Ni0.5Zn0.5Fe2O4 ferrite nanocrystals obtained from reverse microemulsion has been carried out with those obtained from the general chemical co-precipitation route.