Structure, magnetization and magnetoelectric properties of double perovskite Y2CoMnO6

The multiferroic property of double perovskite R₂CoMnO₆ (R=Rare Earth) compounds remains controversial. To clarify this problem, Y₂CoMnO₆ was synthesized. Its structure, magnetization and magnetoelectric properties were studied. The lattice parameters of Y₂CoMnO₆ are a = 5.2362(3) Å, b = 5.5900(3) Å and c = 7.4750(4) Å, respectively. The monoclinic angle is β = 89.8(1)°. They approach to the values of Lu₂CoMnO₆. The ordered Co^2 +/Mn⁴⁺ cations favor a long-range ferromagnetic coupling, with some glassy phase exists due to the partial disordered Co²⁺/Mn⁴⁺. The absence of anomaly in dielectric constant and dielectric loss curves around the magnetic transition temperature suggests that Y₂CoMnO₆ is a typical paraelectric material. The observed pyroelectric current and polarization are thus attributed to the domain wall effect. I.e., from paramagnetic state to ferromagnetic state, the Co²⁺-Mn⁴⁺ bonds and Mn⁴⁺-Co²⁺ bonds carry opposite electric dipole. In electric field, the reverse of the domain walls can establish a net electric polarization. Finally, a detectable pyroelectric current is resulted. Both the magnetic domain and freezing spin play a role in the magnetodielectric coupling of Y₂CoMnO₆. The reverse of magnetic domain tends to decrease the dielectric permittivity, while the flip of the freezing glassy component has a positive contribution to the capacitance.