Synthesis, studies and growth mechanism of ferromagnetic NiFe2O4 nanosheet

Nickel ferrite (NiFe2O4) nanoparticles were prepared by a simple and cost-effective method using nickel nitrate, ferric nitrate, ethylene glycol and citric acid via polyvinylpyrrolidone (PVP) assisted sol-gel auto-combustion method. The structure, composition, morphology and magnetic properties of the gel precursor were characterised XRD confirmed the formation of single phase NiFe2O4 with space group Fd3 m and inverse spinel structure and the crystallite size was found to be 29 nm. The FT-IR showed absorption bands, which were assigned to the vibration of tetrahedral and octahedral complexes. The thermal decomposition of the gel precursors was investigated by TGA. HR-SEM and TEM images showed sheet-like nanostructure. The magnetic properties of these nanosheets were studied for the enlightening ferromagnetic behaviour at room temperature. The magnetic saturation (Ms = 41.70 emu g−1), remanent magnetisation (Mr = 7.57 emu g−1) and coercive force (Hc = 162.47 Oe), were determined.

The morphology of the as-prepared sample is determined by HR-SEM, TEM and HRTEM. The morphology of the as prepared NiFe2O4 is sheet-like structure. HR-TEM shows clear lattice fringes of each nanoparticle. This is interpreted as oriented attachment and sample as sheet-like morphology. From the HR-TEM observations of single sheet-like nanostructures, and the fringe spacing is measured to be 0.291 nm and 0.0.248 nm, which confirms that the nanosheet is single crystal with lattice fringes being (2 2 0) and (3 1 1) planes.Highlights► Single-phase NiFe2O4 powders have been synthesised by a wet chemical route. ► XRD, FTIR, TGA, HR-SEM, TEM, HR-TEM and VSM study. ► The structural and magnetic properties of NiFe2O4 nanosheet. ► PVP plays an important role for the formation of the sheet-like nanostructure. ► Both TEM and HR-SEM image for NiFe2O4 nanocomposite shows the sheet-like nanostructure.