Anomalous Magnetoelectric Coupling in the Paramagnetic State of a Chiral and Polar Magnet

Chiral magnets are excellent platforms for studying intertwined spin, charge, orbit, and lattice degrees of freedom in solid-state materials. In this work, the anomalous magnetoelectric behavior in a chiral magnet K₂Co₂(SO₄)₃ is demonstrated using comprehensive experimental probes. This material adopts a P2₁3 chiral cubic structure at room temperature. Based on the results of high-resolution synchrotron X-ray diffraction, this study shows that the low-temperature (<130 K) crystal structure is a P2₁ monoclinic phase, both polar and chiral. Magnetic and thermodynamic measurements reveal highly frustrated magnetic interactions and possible non-collinear antiferromagnetic ordering at an extremely low temperature ≈0.6 K. Critically, anomalous magnetoelectric correlations are experimentally detected in its paramagnetic temperature regime, which can arise from the synergetic interplay between magnetoelastic and piezoelectric effects. These findings thus indicate that K₂Co₂(SO₄)₃ is a unique material, displaying multiple emergent structural and magnetic phenomena. This is attributed to both its overall crystallographic symmetry and the fact that its magnetic ions are located at low-symmetry sites.