Standard: MMPA - SFG
SOFT FERRITES, A USER´S GUIDE
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INTRODUCTION TO SOFT FERRITES
In the early days of the electrical industry, the need for magnetic materials was served by iron and its magnetic alloys. However, with the advent of higher frequencies, the standard techniques of reducing eddy current losses, using lamination or iron powder cores, were no longer efficient or cost effective.
This realization stimulated a renewed interest in "magnetic insulators" as first reported by S. Hilpert in Germany in 1909. It was readily understood that if the high electrical resistivity of oxides could be combined with desired magnetic characteristics, a magnetic material would result that was particularly well suited for high frequency operation.
Research to develop such a material was being done in various laboratories all over the world, such as by V. Kato, T. Takei, and N. Kawai in the 1930's in Japan and by J. Snoek of the Philips' Research Laboratories in the period 1935-45 in the Netherlands. By 1945 Snoek had laid down the-basic fundamentals of the physics and technology of practical ferrite materials. In 1948, the Neel Theory of ferrimagnetism provided the theoretical understanding of this type of magnetic material.
Ferrites are ceramic, homogeneous materials composed of various oxides with iron oxide as their main constituent. Ferrites can have several distinct crystal structures. However, for this brochure, we are only concerned with the magnetitally soft ferrites, which have a cubic crystal structure.
Based upon the chemical composition, soft ferrites can be divided into two major categories, manganese-zinc ferrite and nickel-zinc ferrite. In each of these categories many different MnZn and NiZn material grades can be manufactured by changing the chemical composition or manufacturing technology. The two families of MnZn and NiZn ferrite materials complement each other and allow the use of soft ferrites from audio frequencies to several hundred megahertz.
The first practical soft ferrite application was in inductors used in LC filters in frequency division multiplex equipment. The combination of high resistivity and good magnetic properties made these ferrites an excellent core material for these filters operating over the 50-450 kHz frequency range.
The large scale introduction of TV in the 1950's was a major opportunity for the fledgling ferrite industry. In TV sets, ferrite cores were the material of choice for the high voltage transformer and the picture tube deflection system.
For four decades ferrite components have been used in an ever widening range of applications and in steadily increasing quantities.
|Organization:||Magnetic Materials Producers Association|
|Most Recent Revision:||YES|
|Document #||Change Type||Update Date||Revision||Status|
|SFG||Change Type:||Update Date: 1992-01-01||Status: INAC|