Multiferroicity in the spin-1/2 quantum matter of LiCu2O2

TL;DR

This study investigates multiferroicity in LiCu2O2, revealing complex magnetic transitions and spin structures that influence ferroelectricity, with unexpected temperature-dependent correlation length behavior.

Contribution

It provides new insights into the magnetic and electric properties of LiCu2O2, highlighting the interplay of frustration and polarization in quantum spin-1/2 materials.

Findings

Identification of two magnetic transitions at 24.6 K and 23.2 K.

Observation of sinusoidal and helicoidal spin structures.

Increase in spin correlation lengths with temperature above T2.

Abstract

Multiferroicity in LiCu2O2 single crystals is studied using resonant soft x-ray magnetic scattering, hard x-ray diffraction, heat capacity, magnetic susceptibility, and electrical polarization. Two magnetic transitions are found at 24.6 K (T1) and 23.2 K (T2). Our data are consistent with a sinusoidal spin structure at T2<T<T1 and with a helicoidal spin structure at T<T2 giving rise to ferroelectricity. Surprisingly, above T2 the correlation lengths of the spin structures increase as the temperature increases with dramatic changes of ~42% along the c-axis. Our results demonstrate the interplay of the geometrical frustration and the electronic and magnetic polarizations.