The Influence of Al+++ Substitution for Fe+++ in M-Type Ba Ferrite Powder on the Intrinsic Coercivity HcJ

Abstract
The influence of Al+++ Substitution for Fe+++ in M-type Ba ferrite on the magnetocrystalline anisotropy field H A and the critical single-domain radius R c has been studied by Haneda and Kojima. It is difficult to obtain H cJ values agreeing with theoretical results for the reason that the H cJ is very sensitive to the preparation method. We have been developing a new method called “coprecipitation combined with high-temperature melting.” It offers a suitable condition for studying the rule of H cJ of Ba Fe12-x Al x O19. Our results conformed to the effects calculated by Haneda and Kojima. The highest level of H cJ in our experiment reached 16000 Oe. We have fabricated plastic sheet magnets from the superhigh H cJ ferrite powder and padded the soft ferrite core with this sheet magnet to adjust the bias magnetic field. This ferrite core can be improved and the weight and size of the device can be reduced.

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