Effects of HfO2 dopant on the structure, magnetic and electrical properties of NiZnCo ferrites.

Abstract HfO 2 doped NiZnCo bulk ferrites, Ni 0.5 Zn 0.3 Co 0.2 Fe 2 O 4 with different HfO 2 dopant content (0 ≤ x ≤ 0.1 wt %), were fabricated by the solid states reaction method. We investigated the influence of HfO 2 doping on structure and electromagnetic properties. The XRD pattern shows that as the doping of HfO 2 increases, the lattice parameter decreases and the X-ray density increases. There is an extra peak in each sample due to generation of NiCo 2 O 4 impurity phase. The SEM images demonstrate the grain size slightly decreases with increasing HfO 2 content. As the amount of HfO 2 doping increases, the saturation magnetization increases linearly and the coercivity decreases. The polarization of all ferrite samples is due to the fact that the electronic hopping frequency between Fe2+ and Fe3+ ions can't keep up with external applied frequency. As the amount of HfO 2 doping increases, the dielectric constant increases when x < 0.075, and decreases when x ≥ 0.075. The peak value frequency dependent behavior of dielectric loss tangent is observed in pure and HfO 2 doped NiZnCo ferrite samples around 1 MHz, which is due to the fact that the electron exchange frequency is consistent with the applied frequency. The DC (direct-current) resistivity decreases exponentially as the temperature increasing, it decreases when x < 0.075 and increases when x ≥ 0.075 as the amount of HfO 2 increasing. [ABSTRACT FROM AUTHOR]