Toroidal order in crystals

Abstract A new ordered state characterized by non-zero toroidal moment density is described. A review of its electrical and magnetic properties is presented. A second order phase transition to the toroidal state is accompanied by Curie-Weiss behavior of a new type of response function, the toroidal susceptibility, which describes the response to an external current. The toroidal state can be either of spin or of orbital nature. Orbital toroidal magnetics can possess large diamagnetism. Key Words: Toroidal momentorder parameterphase transitionmagnetoelectric effectenergy spectrumdiamagnetism