Throughout history, magnetism has seemed a mysterious phenomenon. The discovery of lodestone (Fe3O4) led to many myths (Figure 22.1). Probably the first real use of the magnetic phenomenon should be attributed to the Vikings. Their development of the magnetic compass enabled them to travel far at sea even in foggy conditions. The term magnetic behavior usually means ferromagnetic behavior. There are actually two other types of magnetic behavior: diamagnetic behavior, which is a weak repulsion of a magnetic field, and paramagnetism, which is a weak attraction of a magnetic field.
Ferromagnetism, in contrast, is a strong attraction of a magnetic field. There are only a few ferromagnetic elements. The important ones are iron, nickel, and cobalt. A few rare earths are ferromagnetic at low temperatures. Table 22.1 lists all of the ferromagnetic elements and the temperature above which they cease to be ferromagnetic (Curie temperature).