Development of temperature-independent square-loop ferrites

A series of cobalt-substituted nearly stoichiometric nickel-zinc ferrites was investigated in order to develop a temperature independent square-loop ferrite which also had minimum magnetic noise. In particular the effect of nickel-zinc ratio, cobalt content, and sintering conditions on the temperature stability and on Barkhausen noise were studied. The optimal material showed no temperature dependence of coercive force between 0 and +75°C and had less noise than manganese-magnesium and lithium ferrites. A marked difference was observed between quenched and slow-cooled samples. Interpretation of the experimental results is based on the effects of cobalt on the crystalline and induced anisotropies in nickel-zinc ferrites.