Magnetoelectric Properties of (Ca1−xSrx)2CoSi2O7 Crystals

We have investigated the magnetoelectric properties of (Ca1−xSrx)2CoSi2O7 (0 ≤ x ≤ 1) crystals with a quasi-two-dimensional structure. In Ca2CoSi2O7 (x = 0), a canted antiferromagnetic transition occurs at 5.6 K. The transition temperature TN is increasing with increasing Sr concentration, and the rises of the magnetization and dielectric constant become larger. Since the dielectric constant shows large change at TN and the magnetocapacitance effect is observed below TN, a coupling between the magnetism and dielectricity is strong in (Ca1−xSrx)2CoSi2O7. The positive magnetocapacitance is reduced by Sr substitution, and is not observed in x ≥ 0.5. Namely, the compound of x ≥ 0.5 does not show the magnetic-fieldinduced electric polarization. On the other hand, the negative magnetocapacitance is enhanced by Sr substitution.