Preparation and Properties of Low-Loss Ferrites

Abstract

Nickel-zinc ferrites containing 1–3 mole % cobalt ferrite and small additions of molybdenum oxide or vanadium oxide have been prepared with ${\mu }_{0}Q$ products ranging from 50 000 at 1.0 Mc to 4500 at 60 Mc. The effect of stoichiometry, ferrous iron content, firing temperature, and firing time on the initial permeability ${\mu }_0$ and the magnetic quality factor $Q$ is discussed. It is believed that a necessary condition for good high-frequency response is the domination of the resonance phenomena by a spin-rotation mechanism in preference to a domain-wall process. The nickel ferrite-zinc ferrite system appears to be unique in this respect. In properly constituted nickel-zinc ferrites, low-loss characteristics are achieved by combining a relatively high density with a low magnetocrystalline anisotropy and a very small grain size. The properties in general are intimately related to the Perminvar characteristics these compositions possess, and are interpreted in terms of the Néel-Taniguchi theory.