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

TL;DR

This study explores the magnetoelectric properties of Co2SeO3Cl2, a polar, buckled honeycomb magnet, revealing multiple magnetic transitions and persistent spin fluctuations, highlighting its potential for coupling magnetic and electric dipoles.

Contribution

It introduces Co2SeO3Cl2 as a new magnetoelectric material with unique magnetic transitions and preserved crystallographic symmetry, expanding the understanding of polar honeycomb magnets.

Findings

Multiple magnetic transitions at 25.4, 16.8, 11, and 3 K.

Persistent spin fluctuations indicated by magnetic entropy.

Crystallographic symmetry remains intact across transitions.

Abstract

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.