The history of ferrites (magnetic oxides) began centuries before the birth of Christ with the discovery of stones that would attract iron. The most plentiful deposits of these stones were found in the district of Magnesia in Asia Minor, hence the mineral’s name became magnetite (Fe3O4).
Much later, the first application of magnetite was as ‘Lodestones’ used by early navigators to locate magnetic North. In 1600 William Gilbert published De Magnete, the first scientific study of magnetism. In 1819 Hans Christian Oersted observed that an electric current in a wire affected a magnetic compass needle. With further contributions by Faraday, Maxwell, Hertz and many others, the new science of electromagnetism developed.
Naturally occurring magnetite is a weak ‘hard’ ferrite. ‘Hard’ ferrites possess a magnetism which is essentially permanent. In time, man-made ‘hard’ ferrites with superior properties were developed but producing an analogous ‘soft’ magnetic material in the laboratory proved elusive.
During the 1930’s research on ‘soft’ ferrites continued, primarily in Japan and the Netherlands. However, it was not until 1945 that J. L. Snoek of the Phillips Research Laboratories in the Netherlands succeeded in producing a ‘soft’ ferrite for commercial applications. Originally manufactured in a few select shapes and sizes, primarily for inductor and antenna applications, ‘soft’ ferrite has proliferated into countless sizes and shapes for a multitude of uses. Ferrites are used predominately in three areas of electronics: low level applications, power applications, and Electro-Magnetic Interference (EMI) suppression.
The breadth of application of ferrites in electronic circuitry continues to grow. The wide range of possible geometries, the continuing improvements in material characteristics and their relative cost-effectiveness make ferrite components the choice for both conventional and innovative applications.