Ferromagnetism is the physical phenomenon of spontaneous magnetization in certain materials, most notably iron, cobalt and nickel. It is the strongest type of permanent magnetism and can be found in magnets used in everything from computers to MRI machines. Ferromagnetic materials are also used in electric motors and generators.
The word “ferromagnetism” comes from the Latin ferrum (iron) and magneticus (having to do with magnets). The term was first used by French physicist Pierre Curie in 1857. In 1906, Danish physicist Niels Bohr proposed a model for ferromagnetism that is still used today.
Ferromagnets are different from other types of magnets because they have what is called a “magnetic moment” or “magnetization.” This means that the atoms in a ferromagnetic material are aligned so that their north poles point in the same direction. When this happens, the atoms act like tiny bar magnets and create a strong magnetic field.
The strength of this magnetic field depends on how much of the material is magnetized. For example, a small piece of iron will have a much weaker magnetic field than a large piece of iron. The more atoms that are aligned, the stronger the magnetic field will be.
Some materials, like iron, can be easily magnetized because their atoms are already partially aligned. Others, like cobalt and nickel, need to be exposed to an external magnetic field before they become magnetized. This process is called “magnetic ordering” and it’s what gives ferromagnets their unique properties.