Magnetodielectric coupling in Co/Mn compensated Ca₃Co_1+xMn_1-xO₆ compounds

A series of Co/Mn compensated Ca₃Co_1+xMn_1-xO₆ compounds were synthesized. The structure and magnetization were characterized, as well as the dielectric properties were studied. In Co/Mn compensated samples, the well-ranked Co/Mn ionic order is destroyed which manifests the suppression of the formation of the short-range magnetic order. As a result, the freezing anomaly around T_f = 150 K diminishes. For the two Co/Mn compensated samples, the critical field H_SF that causes magnetic structure change from ↑↑↓↓ state to ↑↑↓↑ state also increases. The appearance of dielectric peak at the antiferromagnetic phase transition temperature clearly indicates the coupling effect between the spin dipole and electric dipole. The temperature corresponding to the dielectric peak increases with the increasing measurement frequency. The frequency dependence of ferroelectric peak identifies relaxor ferroelectric nature. In dielectric measurements associated with magnetic fields, Δε` and Δtanδ have the same sign elucidating intrinsic magnetodielectric effect of Ca₃Co_1+xMn_1-xO₆. For the Co/Mn compensated x = ±0.05 two samples, the suppressed magnetic short-range order also leads to a low diffusion exponent γ and the weak relaxor ferroelectric nature. The thermal activation process of the dipole response is characterized by the Vogel–Fulcher equation and the results confirm that the freezing process of Ca₃Co_1+xMn_1-xO₆ is mainly dominated by coupling of polar nanodomains.