Helicoidal magnetic order in a clean copper oxide spin chain compound

L. Capogna; M. Mayr; P. Horsch; M. Raichle; R. K. Kremer; M. Sofin; A. Maljuk; M. Jansen; B. Keimer

doi:10.1103/PhysRevB.71.140402

paper

Helicoidal magnetic order in a clean copper oxide spin chain compound

arXiv:cond-mat/0411753 · doi:10.1103/PhysRevB.71.140402

Abstract

We report susceptibility, specific heat, and neutron diffraction measurements on NaCu $_{2}$ O $_{2}$ , a spin-1/2 chain compound isostructural to LiCu $_{2}$ O $_{2}$ , which has been extensively investigated. Below 13 K, we find a long-range ordered, incommensurate magnetic helix state with a propagation vector similar to that of LiCu $_{2}$ O $_{2}$ . In contrast to the Li analogue, substitutional disorder is negligible in NaCu $_{2}$ O $_{2}$ . We can thus rule out that the helix is induced by impurities, as was claimed on the basis of prior work on LiCu $_{2}$ O $_{2}$ . A spin Hamiltonian with frustrated longer-range exchange interactions provides a good description of both the ordered state and the paramagnetic susceptibility.

4 pages, 4 figures Improved Fig.1 and 4. Minor rephrasing. Reference added