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.