Effect of Neodymium on the Magnetic and Dielectric Properties of Nickel-cobalt Ferrite

We investigate the effect of Nd doping on the magnetic and dielectric properties of nickel-cobalt ferrite. The samples were synthesized by sol-gel method and structural phase was determined by powder X-ray diffraction technique. X-ray diffraction studies reveal that the cubic spinel structure with space group Fd-3m is maintained for all the compositions. Doping with Nd atoms modified both the magnetic and dielectric properties of nickel-cobalt ferrite. A decrease in saturation magnetization and effective magnetic moment per atomic site is observed with increase in neodymium concentration. The doping of Nd into the Ni-Co ferrite lattice results in enhancement of coercivity and reduction of Curie temperature. The dielectric studies showed an increase in dielectric constant and decrease in loss tangent with the increase in Nd concentration. The frequency dependent dielectric measurements at room temperature were observed to obey the modified Debye model with a relaxation time of the order of 10⁻⁴ s and spreading factor in the range 0.47-0.69. The observed resonance relaxation peaks shift towards lower temperature with increase in Nd concentration.