Temperature Dependence of Anisotropy
The magnetocrystalline anisotropy parameters have a strong dependence on temperature. They generally decrease rapidly as the temperature approaches the Curie temperature, so the crystal becomes effectively isotropic. Some materials also have an isotropic point at which K1 = 0. Magnetite (Fe3O4), a mineral of great importance to rock magnetism and paleomagnetism, has an isotropic point at 130 kelvin.
Magnetite also has a phase transition at which the crystal symmetry changes from cubic (above) to monoclinic or possibly triclinic below. The temperature at which this occurs, called the Verwey temperature, is 120 Kelvin.
Read more about this topic: Magnetocrystalline Anisotropy
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