Linear magnetoelectric effect in antiferromagnetic Sm2BaCuO5

We report the discovery of linear magnetoelectric effect in the well-known green-phase compound, Sm2BaCuO5, which crystallizes in the centrosymmetric orthorhombic (Pnma) structure. Magnetization and specific heat measurements reveal the long-range antiferromagnetic ordering of Cu2+- and Sm3+ ions moments at T-N1 = 23 K and T-N2 = 5 K, respectively. Applied magnetic field induces dielectric anomaly at T-N1 whose magnitude increases with field, which results in significant (1.7%) magnetocapacitance effect. On the other hand, the dielectric anomaly observed in zero-applied magnetic field at T-N2 shows a small (0.4%) magnetocapacitance effect. Interestingly, applied magnetic field induces an electric polarizaiton, below T-N1, that varies linearly up to the maximum applied field of 9 T with the magnetoelectric coefficient alpha similar to 4.4 ps/m, demonstrating high magnetoelectric coupling. Below T-N2, the electric polarization decreases from 35 to 29 mu C/m(2) at 2 K and 9 T due to ordering of Sm sublattice. The observed linear magnetoelectricity in Sm2BaCuO5 is explained using symmetry analysis.