Investigation on size dependent structural and magnetic behavior of nickel ferrite nanoparticles prepared by sol–gel and hydrothermal methods

In the present article, we report the synthesis of Nickel ferrite (NiFe2O4) nanoparticles using sol–gel and hydrothermal methods. In the sol–gel synthesis process we used glycolic acid as a chelating agent for the preparation of NiFe2O4 nanoparticles. In this process, glycolic acid acts as a fuel which decomposes the metal complexes at low temperature and yields impurity free NiFe2O4 nanocrystalline structures. In the hydrothermal process the NiFe2O4 nanoparticles were synthesized at low temperature (∼160 °C). The size of NiFe2O4 nanoparticles obtained through hydrothermal process was smaller (∼9 nm) than that of sol–gel process (∼27 nm). The synthesized nanoparticles were characterized by thermogravemetric analysis (TGA)/differential scanning calorimetery (DSC), Fourier Transform Infrared (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy and vibrating sample magnetometer (VSM). The magnetic measurements of nanoparticles were done at room temperature and found that NiFe2O4 nanoparticles synthesized by sol–gel method exhibit a ferromagnetic behavior with a saturation magnetization 31 emu g−1 while the NiFe2O4 nanoparticles synthesized by hydrothermal process exhibit a superparamagnetic behavior with a saturation magnetization of 46 emu g−1.