• What is the history of permanent magnets in east

    Man-shaped compass mounted on a chariot

    Man-shaped compass mounted on a chariot

    The first reported application of naturally occurring permanent magnet material is in the Chinese chronicles. It has been reported 2 that the best prepared caravans that crossed the Gobi desert, from the minarets of the kingdoms of the Kushans to the imperial pagodas on the banks of the Yangtze, contained a white camel. In a clay pot full of water, protected by a carved wooden box mounted between the humps of the albino beast, floated a cork containing a piece of magnetized iron. The edges of the pot were painted in four colors: red for south, black for north, green for east and white for west. This primitive compass enabled the caravaner to navigate across the sands. In the Chinese chronicles there are also descriptions of magnetic gates, which restricted the access of armed ill wishers, and magnetic roadways made possible by the magic stone chu-shih. These stones, simply magnetic iron ore, were also known as ‘loving stones’ because their attraction for pieces of iron was similar to the love parents have for their children.

    One Chinese legend relates that Emperor Huang-Ti, nearly 5000 years ago, had a chariot made on which was mounted a small man with an outstretched arm. This arm, Figure 1, always pointed South, so that Huang-Ti’s armies were able to attack their enemies from the rear in a fog and defeat them.

    Chinese spoon compass

    Chinese spoon compass

     

    The stories of camel and chariot mounted compasses may be apocryphal, but Chinese encyclopedias state that magnetic needles were used as compasses on ships in 400 BC, and there exists a 1000 year old Chinese compass resembling a traditional painted spoon, see Figure 2.

    Notwithstanding these early oriental excursions into permanent magnetism, the principal development of permanent magnet materials has been undertaken in Europe.

  • The history of Permanent magnets in Europe

    A naturally occurring permanent magnet material, a variety of magnetite, Fe3O4, known as a lodestone was known to the Greeks. The name lodestone, or alternatively and incorrectly loadstone, was derived from its navigational property of seeking the lodestar. The names magnetite, magnetism and all their derivatives stem from the name of the district where lodestones were found to be plentiful, Magnesia. The microstructural origin of the coercivity of lodestones, typically 10 kA/m, was shown to be due to a fine intergrowth of Fe2O3produced by oxidation in the Fe3O4material. This fine microstructure acts as an in homogeneity impeding magnetic reversal, by restricting the motion of the magnetic domain walls, thereby increasing the coercivity of the material. Thales of Miletus, circa600 BC, and many other Greek philosophers of the period from 400 to 200 BC described the attractive property of lodestones. Later, Lucretius in “De natura reru” described the repulsion of lodestones, but it was the development of artificial permanent magnets made by ‘touching’ iron needles with a lodestone which was the first transition in the improvement of permanent magnet materials. It is not possible to locate accurately the first production of artificial permanent magnets. At the beginning of the 13th century, the French troubadour Guyot de Provins called Hugue de Bercy by Hoppe 6describes, in
    his satirical poem “La Bibl,” the use of a touched needle in a straw floating on water. It is claimed that the inhabitants of Amalfi particularly the jeweler Flavio Gioia made compasses, similar to today’s instruments with a rotating disc marked out in divisions, at the beginning of the 13th century. Peter Peregrinus, in his famous treatise “Epistola and Sygerum de Foucoucourt milite de magnet,” in 1269, stated that an oblong piece of iron which had been touched by a lodestone would turn toward the pole if floated on a piece of wood. He also discovered that two regions of the magnetite, now called magnetic poles, attracted a piece of iron more strongly then the rest of the magnetite. During the next three centuries, the alchemists attempted to develop lodestones as a facilitator for the change of base metal into gold, as an aphrodisiac, as a talisman to attract the opposite sex, etc. This extensive period, which produced no improvements in the properties of permanent magnets, was terminated by the publication of the first great work in the field of magnetics.