Co2SeO3Cl2: Studies of Emerging Magnetoelectric Coupling in a Polar, Buckled Honeycomb Material

The development of magnetoelectric materials requires chemical design strategies that integrate structural polarity with magnetic lattices capable of supporting competing spin interactions. Here, we demonstrate such an approach in the polar, buckled honeycomb magnet Co2SeO3Cl2. Magnetization and heat-capacity measurements reveal strong magnetic anisotropy and four successive magnetic transitions at 25.4, 16.8, 11, and 3 K. The recovered magnetic entropy through the ordering regime is only around half of the expected 2Rln(2), indicating persistent spin fluctuations. Second-harmonic generation measurements show three pronounced intensity anomalies at 11, 17, and 26 K that coincide with magnetic transitions while revealing that the crystallographic symmetry is preserved. Together, these results demonstrate that polar, buckled honeycomb magnets offer an unconventional phase space for coupling magnetic and electric dipoles in magnetoelectric materials.

💡 Research Summary

This paper reports the design, synthesis, and comprehensive characterization of a new polar, buckled‑honeycomb magnet, Co₂SeO₃Cl₂, which the authors propose as a promising platform for magnetoelectric coupling. The material crystallizes in the non‑centrosymmetric monoclinic space group P2₁. Two crystallographically distinct Co²⁺ sites (Co(1) and Co(2)) form a buckled honeycomb network within the ac‑plane, each coordinated by three O atoms from SeO₃²⁻ groups and three Cl⁻ ions, giving rise to distorted, polar