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.
