Studies of Multiferroic System LiCu2O2 I Sample Characterization and Relationship between Magnetic Properties and Multiferroic Nature

TL;DR

This study characterizes LiCu2O2 single crystals, revealing magnetic transitions and clarifying that multiferroic behavior occurs only below 22.8 K, excluding lattice defects as the cause.

Contribution

It provides detailed structural and magnetic analysis of LiCu2O2, linking magnetic transitions to multiferroic properties and confirming the absence of lattice defects.

Findings

Magnetic transitions at 24.5 K and 22.8 K identified.

Multiferroic properties only appear below 22.8 K.

Lattice defects are not responsible for multiferroic behavior.

Abstract

Single-crystal samples of LiCu2O2 with spin 1/2 Cu2+ chains of edge-sharing CuO4 square planes (ribbon chains), have been characterized by X-ray diffraction, thermogravimetric analysis, and magnetic measurements. Neither the atomic deficiency nor the mixing of Cu and Li atoms has been found, indicating that lattice defects conceived as a possible origin of the reported multiferroic behavior can be excluded. Anomalies found in the data of specific heat and neutron magnetic Bragg reflections show clear evidence that the system exhibits successive magnetic transitions at TN1=24.5 K and TN2=22.8 K. Based on the magnetic structures in the intermediate (TN2<T<TN1) and low temperature (T<TN2) phases, determined by the combined studies of neutron scattering and 7Li-NMR measurements, we can consistently understand the fact that the multiferroic properties are observed only below TN2 by considering existing theories.