The effect of cobalt substitutions on some properties of manganese zinc ferrites

The effect of cobalt substitutions in manganese zinc ferro ferrites for inductor applications is discussed. Permeability-temperature curves are presented over the range -50 degrees C to 200 degrees C for compositions where the cobalt level is varied between 0 and 0.010 per formula unit, the Mn/Zn ratio and Fe 2+ level being held constant at 3.5 and 0.105 per formula unit respectively. The anisotropy compensation model fails to give a satisfactory explanation of the above curves since the materials exhibit a uniaxial anisotropy, the degree of which is dependent on the thermal history of the samples. The effect causes the permeability to be unstable in time and the resulting high disaccommodation makes application of such materials unlikely.