Rare Earth Magnets
The word magnet landed in English via the Latin magnes, which is derived from the Greek magnēs lithos meaning a stone (lodestone) from Magnesia, a Greek city. Permanent magnets in the form of lodestone, a naturally-occurring weak magnet, were known to the Ancient Chinese, Romans, Greeks and, presumably, to other ancient societies. Lodestone consists mainly of ferrimagnetic magnetite (Fe3O4) with inclusions of ferromagnetic maghemite (γ-Fe2O3) that have been magnetized: interestingly, not all naturally-occurring magnetite has been magnetized. Although the magnetized lodestone could be shown to attract iron, Ancient Peoples made no practical use of these permanent magnets. The first practical use of a permanent magnet had to wait until eleventh century China (the Song dynasty) when a mariner’s compass was developed that used a magnetized iron needle. The best current permanent magnets are the so-called Rare Earth Magnets.
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