Anisotropic spin-flip-induced multiferroic behavior in kagome Cu3Bi(SeO3)2O2Cl

Compared to the previous report on Cu3Bi(SeO3)(2)O2X (X = Cl, Br) [V. Gnezdilov et al., (arXiv: 1604.04249)], where no dielectric anomaly was observed without magnetic field near T-N similar to 25.6K, we further present the dielectric behaviors without and with magnetic field in Cu3Bi(SeO3)(2)O2Cl. At zero field H = 0, an antiferromagnetic transition from magnetization and specific heat measurements is clearly established at T-N, while no dielectric anomaly was observed. Those results are similar to the previous report [V. Gnezdilov et al., (arXiv: 1604.04249)]. Above the critical field H-c similar to 0.8 T, a metamagnetic spin-flip transition from antiferromagnetic to ferrimagnetic order at T similar to T-N is induced anisotropically only for H broken vertical bar broken vertical bar c. Meanwhile, a ferroelectric behavior from dielectric and pyroelectric current measurements is observed below T similar to T-N; then a corresponding type-II multiferroics emerges above H-c. The key mechanism of the anisotropic spin-flip-induced multiferroicity in Cu3Bi(SeO3)(2)O2Cl can be ascribed to the breaking of magnetic twofold symmetry in the bc plane above H-c.