Enhanced Magnetic Permeability in Ni{sub 0.55−y}Co{sub y}Zn{sub 0.35}Mg{sub 0.10}Fe{sub 2}O{sub 4} Synthesized by Sol-Gel Method

Growth in permeability with increasing cobalt content in Ni-Zn ferrite is a rare phenomenon. The rise in magnetic anisotropy associated with the cobalt, in general, suppresses the relative permeability of the material. However, cobalt substituted nickel-zinc ferrite of composition, Ni{sub 0.55−y}Co{sub y}Zn{sub 0.35}Mg{sub 0.10}Fe{sub 2}O{sub 4} (y= 0.00, 0.04, 0.08, 0.12, 0.16, 0.20), synthesized by sol-gel method, showed an enhanced relative initial permeability from 100 to 220 in the frequency range 60 Hz to 50 MHz with increasing cobalt content. The factors causing the permeability increase have been discussed in terms of the observed variations in particle size, saturation magnetization, and Curie temperature. The magnetization process under the influence of cobalt has been illustrated in detail with the help of dM/dH versus magnetization curves.