Effect of Ni doping on structural, magnetic and dielectric properties of M-type barium hexaferrite

Polycrystalline samples of BaFe12-xNixO19 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared in single phase form by sol-gel method and their magnetic and dielectric properties were investigated. The frequency variations of impedance spectroscopy were analyzed to understand the relaxation mechanism due to thermal activation of charge carriers across the grains and grain boundaries. The dielectric constant is found to increase with increase in Ni concentration, whereas the loss tangent decreases with Ni doping. The temperature variation of magnetization measurement reveals that the ferrimagnetic transition temperature (Tc) increases with Ni doping from 720 K for x = 0-759 K for x = 0.5. With increase in Ni concentration, the saturation magnetization value at room temperature is found to decrease from 68.16 emu/g for x = 0-58.99 emu/g for x = 0.5 sample.