Second-Order Susceptibility Terms in Orthoferrites at Room Temperature

Two possible mechanisms for weak ferromagnetism, single-ion magnetocrystalline anisotropy and antisymmetric exchange, are examined on orthoferrites which contain a paramagnetic rare earth. The study was done by comparing the ferromagnetic components and the terms of the second-order susceptibility tensor that are obtained from torque measurements to the equivalent values calculated from Hamiltonians based on above mechanisms. The results show that the weak ferromagnetism is due mainly to the antisymmetric exchange mechanism.