One pot synthesis of nickel ferrite-graphitic layers nanocomposite with inverted magnetic hysteresis

Abstract For the first time, we report the synthesis of nickel ferrite-graphitic layers nanocomposite (C-NiFe2O4) via a straightforward approach using iron-nickel cyanide powder (Fe[Ni(CN)4]·3H2O). Firstly, iron-nickel cyanide powder was prepared by mixing equal molar amount of iron salt and potassium tetracyanonickelate (II) hydrate. Secondly, the as-synthesized iron-nickel cyanide powder was thermally treated in air at a temperature as low as 400 °C. The ignition starts at one point of high energy like the edges and then propagates like a wave through all the material. The ignition process was accompanied by huge expansion finally forming C-NiFe2O4 nanocomposite. All samples were characterized by the standard characterization techniques such as field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HRTEM), Raman spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) as well as vibrating sample magnetometer (VSM) to probe the magnetic properties at room temperature. HRTEM investigation reveals the presence of the graphitic layer on the nickel ferrite nanoparticles. Iron-nickel cyanide powder which has sheet-like morphology was directly converted into C-NiFe2O4 nanocomposite during the thermal treatment in air. The VSM magnetic investigations revealed unusual inverted hysteresis behavior of the as-prepared C-NiFe2O4 nanoparticles. While traditional hysteresis loop was obtained in the case of iron-nickel cyanide with specific magnetization saturated at 0.142 emu/g, anomalous hysteresis loop was observed in the case of C-NiFe2O4 nanocomposite with specific magnetization saturated at 28.668 emu/g. The mechanism of the C-NiFe2O4 nanocomposite formation has been proposed based on the obtained experimental data. The present approach for the C-NiFe2O4 nanocomposite synthesis is straightforward, surfactant free, simple and scalable as well as it can be applied to the other ferrites.