IMF2017

Thin films of EuTiO₃ deposited on a SrTiO₃ substrate have been fabricated which are insulating and transparent with a band gap of 4.53eV. Both materials are non-magnetic at room temperature. The films have been shown to be single crystalline with the cubic c-axis in the growth direction. At T_S = 282 K, EuTiO₃ changes from cubic to tetragonal symmetry thereby allowing the observation of birefringence Δn caused due to symmetry lowering. Below T*=190K an upturn in the birefringence signals another up to now unknown structural phase transition. Upon applying a magnetic field of only 0.02 T, Δn can be tuned directionally whereby the magnetic field directed along the [110] direction completely suppresses it in contrast to the perpendicular direction [11 ̅0] where it remains active up to 240 K. Along [100] and [010] the onset of Δn is observed below T_S as expected from symmetry considerations. An increase in the magnetic field to 0.1 Tesla leads to an enormous increase in Δn by a factor of 3 and a shift of its onset temperature from 240 K to almost room temperature with the field being aligned along [11 ̅0] direction. In the perpendicular direction an enhancement of both Δn and its onset temperature takes place, however, much less pronounced compared to the [11 ̅0] direction. From these data it is apparent that EuTiO₃ thin films are magneto-optically active and suited for device applications. The magneto-optical properties can be tuned by a magnetic field and temperature together with rotations of the sample and the magnetic field.