Anisotropic magnetodielectric effect in isotropic EuTiO 3 ceramics

EuTiO 3 is an incipient ferroelectric antiferromagnet showing an anomalously strong spin-phonon coupling. We studied EuTiO 3 ceramics by terahertz (THz) time-domain spectroscopy upon varying temperature and magnetic field. We observed a large anisotropy which is due to the shift from the microwave to the sub-THz region of a ferromagnetic resonance appearing only when the external magnetic field is applied perpendicular to the magnetic component of the THz radiation.