Large off-diagonal magnetoelectricity in a triangular Co<sup>2+</sup>-based collinear antiferromagnet.

Xu, Xianghan; Hao, Yiqing; Peng, Shiyu; Zhang, Qiang; Ni, Danrui; Yang, Chen; Dai, Xi; Cao, Huibo et al. · Nat Commun · 2023

basic_science · Level V

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Abstract

Magnetic toroidicity is an uncommon type of magnetic structure in solid-state materials. Here, we experimentally demonstrate that collinear spins in a material with R-3 lattice symmetry can host a significant magnetic toroidicity, even parallel to the ordered spins. Taking advantage of a single crystal sample of CoTe<sub>6</sub>O<sub>13</sub> with an R-3 space group and a Co<sup>2+</sup> triangular sublattice, temperature-dependent magnetic, thermodynamic, and neutron diffraction results reveal A-type antiferromagnetic order below 19.5 K, with magnetic point group -3' and k = (0,0,0). Our symmetry analysis suggests that the missing mirror symmetry in the lattice could lead to the local spin canting for a toroidal moment along the c axis. Experimentally, we observe a large off-diagonal magnetoelectric coefficient of 41.2 ps/m that evidences the magnetic toroidicity. In addition, the paramagnetic state exhibits a large effective moment per Co<sup>2+</sup>, indicating that the magnetic moment in CoTe<sub>6</sub>O<sub>13</sub> has a significant orbital contribution. CoTe<sub>6</sub>O<sub>13</sub> embodies an excellent opportunity for the study of next-generation functional magnetoelectric materials.