High Coercivity Induced in Nickel Ferrite Nanoparticles by Mechanical Milling

Abstract

This work reports a study of the structure and magnetic behavior of NiFe₂O₄ ferromagnetic oxide nanoparticles synthesized by the combustion method. The structural and magnetic properties of nanoparticles after mechanical milling are investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscope. Their structural properties and magnetic behavior are characterized by a vibrating sample magnetometer (VSM). The non-milled sample presents a coercivity of 89 Oe, a saturation magnetization of 69 emu/g, and a remanence of 13 emu/g. After milling, the sample attains the coercivity, the saturation magnetization, and the remanence of 160.7 Oe, 56 emu/g, and 12.8 emu/g respectively. The porosity estimated from the X-ray density and bulk density is about 35%. The XRD analysis by Stokes–Wilson, Williamson-Hall, and dislocation density equations are used to estimate strain and the dislocation density induced by mechanical milling in the sample.