7Li NMR study of the ordering phenomena in the intrinsic two-component magnetoelectric material Li2ZrCuO4

Abstract

We report an experimental and theoretical study of the low temperature 7Li nuclear magnetic resonance (NMR) spectra of oriented powder samples of γ-Li2ZrCuO4 (≡Li2CuZrO4) which comprises interpenetrating sublattices of frustrated quasi-one- dimensional s=1/2 quantum Heisenberg magnetic Cu2+ chains and frustrated quantum Ising electric sublattice of LiI ions. Incommensurate spin order occurring in this compound at TNâ6 K gives rise to a drastic change of the 7Li NMR spectrum. We show that the peculiar NMR line shapes are determined by the specific, sample dependent, distribution of the LiI ions in the glassy ordered electric sublattice. The analysis of the NMR data in the framework of a spin-spiral model gives evidence for a remarkable interaction between magnetic and electric degrees of freedom in γ-Li2ZrCuO4, which suggests it as a promising model compound for fundamental studies of complex magnetoelectric phenomena and illustrates well their richness. © 2013 American Physical Society.