The compositions of Co substituted Ni-Zn ferrites having the formula Ni0.65-xCoxZn0.35Fe2O4 (where x = 0 .0 0 ,
0.01, 0.03, 0.05, 0.07 and 0.09) were prepared by the solid state reaction method and sintered at 1350 oC. The
structural property was observed with X-ray diffraction (XRD) method and it showed the single phase cubic
spinel structure. Saturation magnetization (M
s), experimental magnetic moment (n
exp) and coercive field (H
c)
have been investigated. It was observed that the larger value of M
s was found at x = 0.03 due to its stronger
super-exchange interaction between two sub-lattices in the spinel ferrites. However, M
s decreases for 0.05  x
 0.09 due to the effect of Yafet-Kittle angle. All the compositions are found to be smaller value of H
c, which
indicates the magnetic softness nature of the spinel ferrites. The initial permeabilities were increased which
could be attributed to the densification of the samples.