Complex permeability and power loss measurements on Ni-Zn-In-Ti ferrites

Polycrystalline high saturation magnetization nickel-zinc ferrites with fixed quantity of indium and varied quantities of titanium and zinc with the general formula Ni_0.65Zn_0.35+xIn_0.01Ti_xFe_1.99-2x O₄, where x varies from 0.00 to 0.25 in steps of 0.05, have been prepared by conventional ceramic technique to examine their usefulness for high frequency power applications. Sintering of the samples was carried out at 1250 °C for 4 hours in air atmosphere followed by natural cooling. X-ray diffraction patterns confirm single phase spinel structure in all the samples. Complex permeability measurements exhibit a stable frequency response up to 5 MHz beyond which the real permeability drops and imaginary permeability increases to display a peak around 10 MHz. Power loss density has been observed to be very low up to 3 MHz, however, it increases rapidly beyond 3 MHz; thus it is suggested that these materials could be useful as core materials up to 3 MHz. The results are analysed and discussed in terms of the changes in compositions, microstructure and the associated processes of resonance and relaxation due to domain wall movements and damping of spin rotations contributing to the variations in permeability and losses.