Monocrystalline high-saturation magnetization ferrites for video recording head application: III. CoII doped MnZn ferrites with large FeII contents

Abstract

It is shown that substitution of CoII into FeII-rich MnZn ferrites makes it possible to enlarge the FeII content permissible for combined write/read video recording heads. This results in an increase of the saturation magnetization Ms, which is important when high-coercivity magnetic tapes are used. A properly chosen CoII content compensates the magnetocrystalline anisotropy of the ferrites in such a way that the temperature of the maximum in the magnetic permeability μ′ versus temperature curve, caused by anisotropy compensation by FeII, is lowered to the level at which a recording head operates. We report on monocrystalline ferrites with suitable CoII-FeII concentration combinations, showing Ms values of up to 0.660 T and a maximum in μ′(T) at 40°C of 600–700 at 4.5 MHz. We show that with CoII substitutions, the enlargement of the FeII content does not give rise to larger magnetic disaccommodation effects. The present paper is the third in a series of three dealing with FeII-rich ferrites for video recording head application.