Evaluation of electrical, dielectric and magnetic characteristics of Al–La doped nickel spinel ferrites

Abstract

The paper reports the effects of lanthanum and aluminum ions, on the structural, electrical and magnetic properties of NiFe₂O₄ spinel ferrite nanoparticles. The precursors have been synthesized via a hydrothermal route in the presence of ascorbic acid (AA) using urea as a reducing agent and fuel for maintaining the uniform morphology and equal particle size distribution. In order to find out the optimum temperature (1023 K) for the formation of the spinel phase of the doped nickel ferrite, thermogravimetric analysis (TGA) for the un-annealed samples was performed. The X-ray diffraction patterns show that NiFe_2−2xAl_xLa_xO₄ have been well crystallized to spinel ferrite crystal structure with the Fd3m space group. The average crystallite size obtained is in the range of 9–19 nm, a size useful for attaining a suitable signal-to-noise ratio in high-density recording media and in electrical devices. In order to render the synthesized samples for diminishing eddy current losses, we were able to enhance the room temperature resistivity through proper selection of dopant used. The dielectric constant and dielectric loss decreased with applied frequency for all the samples showing normal behavior of ferrites. The calculated magnetic parameters such as saturation magnetization (M_s), remanence (M_r) and coercivity (H_c), showed increased values for some Al–La doped samples.