Multiferroics

Our concern here is magnetism, but occasionally materials are found to exhibit more than one order parameter at the same time. Besides magnetic order, and its appropriate conjugate field, there are ferroelectrics, which exhibit electrically switchable electric polarization, and ferroelastics, which exhibit stressswitchable elastic strain. A multiferroic material exhibits at least two of these order parameters, and is described by a complicated tensor susceptibility with components of both fields. Ferromagnetism is rarely associated with ferroelectricity, and no material is known for which both magnetic and electric Curie points are above room temperature.