Large off-diagonal magnetoelectric coupling in the quantum paraelectric antiferromagnet EuTiO3

The third-order (EH2)-H-2-type magnetoelectric (ME) response of polycrystalline EuTiO3 changes sign under magnetic bias and shows a large anomaly at the antiferromagnetic (AF)-paramagnetic phase boundary below T-N approximate to 5.3 K. It is attributed to critical fluctuations of the AF order parameter reinforced by quantum paraelectric polar correlations. The underlying biquadratic spin-lattice coupling involves electric field induced Dzyaloshinskii-Moriya interaction as described within mean-field approximation. Single domaining by ME annealing (or cooling) significantly enhances the response by additional EH and EH2 effects.