Magnet
Many materials have unpaired electron spins, and the majority of these materials are paramagnetic. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called ferromagnetic (what is often loosely termed as magnetic). Because of the way their regular crystalline atomic structure causes their spins to interact, some metals are ferromagnetic when found in their natural states, as ores. These include iron ore (magnetite or lodestone), cobalt and nickel, as well as the rare earth metals gadolinium and dysprosium (when at a very low temperature). Such naturally occurring ferromagnets were used in the first experiments with magnetism. Technology has since expanded the availability of magnetic materials to include various man-made products, all based, however, on naturally magnetic elements.
Magnetism
Magnetism was first discovered in the ancient world, when people noticed that lodestones, naturally magnetized pieces of the mineral magnetite, could attract iron. The word "magnet" comes from the Greek term μαγνῆτις λίθος "magnētis lithos", "the Magnesian stone, lodestone." In ancient Greece, Aristotle attributed the first of what could be called a scientific discussion of magnetism to the philosopher Thales of Miletus, who lived from about 625 BC to about 545 BC. The ancient Indian medical text "Sushruta Samhita" describes using magnetite to remove arrows embedded in a person's body.
In ancient China, the earliest literary reference to magnetism lies in a 4th-century BC book named after its author, "The Sage of Ghost Valley".
The 2nd-century BC annals, "Lüshi Chunqiu", also notes:
"The lodestone makes iron approach, or it attracts it."
The earliest mention of the attraction of a needle is in a 1st-century work "Lunheng" ("Balanced Inquiries"): "A lodestone attracts a needle."
The 11th-century Chinese scientist Shen Kuo was the first person to write—in the "Dream Pool Essays"—of the magnetic needle compass and that it improved the accuracy of navigation by employing the astronomical concept of true north.
By the 12th century the Chinese were known to use the lodestone compass for navigation. They sculpted a directional spoon from lodestone in such a way that the handle of the spoon always pointed south.