Ferrimagnetism
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In physics, a ferrimagnetic material is one in which the magnetic moment of the atoms on different sublattices oppose as in antiferromagnetism but the opposing moments are unequal and a spontaneous magnetization remains. This happens when the sublattices consist of different materials or ions (such as Fe2+ and Fe3+).
Ferrimagnetic materials show no magnetic order above the Neel temperature like antiferromagnets and can hold a spontaneous magnetization below it like ferromagnets. However, there is sometimes a temperature below the Neel temperature at which the two sublattices have equal moments, resulting in a net moment of zero, called the compensation point.
The oldest magnetic substance known is the ferrimagnet, magnetite, and it is among the materials that were classified as ferromagnets before Neel's discovery of ferrimagnetism and antiferromagnetism.