Ferromagnets are materials that can become magnetized and retain their magnetic properties even after an external magnetic field is removed. This occurs due to the alignment of magnetic moments of atoms within the material, which can be influenced by temperature and external magnetic fields. Common examples of ferromagnetic materials include iron, nickel, and cobalt. The ability of ferromagnets to maintain magnetization is due to a phenomenon called magnetic hysteresis. When exposed to a magnetic field, the domains within the material align in the direction of the field. Once the field is removed, some of these domains remain aligned, resulting in a permanent magnet.