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Physical phenomenon in which certain electrically uncharged materials strongly attract others. It is associated with iron, cobalt, nickel, and some alloys or compounds containing these elements. It is caused by the alignment patterns of the material's atoms, each of which acts as a simple electromagnet, due to the motion and spin of the electrons. The tiny magnets spontaneously align themselves in the same direction, so their magnetic fields reinforce each other. Ferromagnetic materials are magnetized easily. Above a temperature called the Curie point, they cease to be magnetic, but they become ferromagnetic again upon cooling below the Curie point. See alsoferrimagnetism.
This entry comes from Encyclopædia Britannica Concise. For the full entry on ferromagnetism, visit Britannica.com.