ferrimagnetism

thumb|Ferrimagnetic ordering thumb|Magnetic orders: comparison between ferro, antiferro and ferrimagnetism thumb|Ferrite magnets. Ferrite (magnet)|Ferrite, a [[ceramic compound, is one of the most common examples of a ferrimagnetic material.]] A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude, so a spontaneous magnetization remains. This can, for example, occur when the populations consist of different atoms or ions (such as Fe2+ and Fe3+).

Like ferromagnetic substances, ferrimagnetic substances are attracted by magnets and can be magnetized to make permanent magnets. The oldest known magnetic substance, magnetite (Fe3O4), is ferrimagnetic, but was classified as a ferromagnet before Louis Néel discovered ferrimagnetism in 1948. Since the discovery, numerous uses have been found for ferrimagnetic materials, such as hard-drive platters and biomedical applications.