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.
Exchange spring magnet
The magnetic moment of a bulk material is the sum of all of its atomic moments. The atomic moments' interactions with each other and with the externally applied field determine the behavior of the magnet. Each atomic magnetic moment tries to orient itself so that the total magnetic energy reaches a minimum. There are generally four types of energy competing with each other to reach equilibrium: each is derived from the exchange coupling effect, magnetic anisotropy, the magnetiostatic energy of the magnet, and the magnet's interaction with external field.