Magnetism
Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron, nickel and cobalt and their alloys. The prefix "" refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, FeO.
Rare-earth magnet
The development of rare-earth magnets began around 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that an alloy of yttrium and cobalt, YCo, had by far the largest magnetic anisotropy constant of any material then known. The term "rare earth" can be misleading, as these metals are not particularly rare or precious; they are about as abundant as tin or lead. However rare earth ores are unevenly distributed, with the major source being China, which has led countries to classify rare earth metals as strategically important. Recent Chinese export restrictions on these materials have led other countries to initiate research programs to develop strong magnets that do not require them.