${}^7\mathrm{Li}$ NMR spectra were measured in a magnetic field up to 17 T at temperatures 5–30 K on single crystalline ${\mathrm{LiCu}}_2{\mathrm{O}}_2$. Earlier reported anomalies on magnetization curves correspond to magnetic field values where we observe changes of the NMR spectral shape. For the interpretation of the field and temperature evolutions of our NMR spectra, the magnetic structures were analyzed in the frame of the phenomenological theoretical approach of the Dzyaloshinskii-Landau theory. A set of possible planar and collinear structures was obtained. Most of these structures have an unusual configuration; they are characterized by a two-component order parameter and their magnetic moments vary harmonically not only in direction, but also in size. From the modeling of the observed spectra, a possible scenario of magnetic structure transformations is obtained.

• Received 10 May 2017
• Revised 9 February 2018

DOI:https://doi.org/10.1103/PhysRevB.97.054428