Anisotropic Exchange in $\mathbf{LiC}{\mathbf{u}}_2{\mathbf{O}}_2$

Abstract

We investigate the magnetic properties of the multiferroic quantum-spin system LiCu${}_2$O${}_2$ by electron spin resonance (ESR) measurements at $X$- and $Q$-band frequencies in a wide temperature range $(T_{N1}\le T\le 300$\,K). The observed anisotropies of the $g$ tensor and the ESR linewidth in untwinned single crystals result from the crystal-electric field and from local exchange geometries acting on the magnetic Cu${}^{2+}$ ions in the zigzag-ladder like structure of LiCu${}_2$O${}_2$. Supported by a microscopic analysis of the exchange paths involved, we show that both the symmetric anisotropic exchange interaction and the antisymmetric Dzyaloshinskii-Moriya interaction provide the dominant spin-spin relaxation channels in this material.

10 pages, 10 Figures