Effect of Sr-substitution on the structure, magnetization and electric properties of Ca3CoMnO6 compound

The Sr²⁺ modified Ca_3-xSr_xCoMnO₆ (0 ≤ x ≤ 0.3) compounds were prepared. The replacement of Ca²⁺ by larger Sr²⁺ increases the lattice parameters a and b, but the lattice constant c decreases. It makes the intrachain Co_trig-Mn_oct exchange distance reduce and the intrachain antiferromagnetic coupling enhance. In turn, the correlation length of the short-range magnetic ordering is suppressed. The relaxation of the freezing magnetization becomes quicker. The temperature dependent dielectric permittivity and loss factor confirm the relaxor ferroelectric nature. It suggests the existence of polar nanodomains in Ca_3-xSr_xCoMnO₆ (0 ≤ x ≤ 0.3) compounds. The dynamic behavior of the polar nanodomains well follows the Vogel-Fulcher equation. The lower diffusion exponent γ of the doped samples implies that replacement of Ca²⁺ by Sr²⁺ is an effective way to improve the ferroelectricity of Ca₃CoMnO₆. For the parent Ca₃CoMnO₆, the magnetoelectric coupling effect is mainly contributed by the reorientation of Co²⁺-Mn⁴⁺ dipole. With introducing Sr²⁺ dopant, Maxwell-Wagner effect plays the more and more pronounced role.