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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
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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.

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L. Capogna, M. Mayr, P. Horsch, M. Raichle, R. K. Kremer, M. Sofin, A. Maljuk, M. Jansen, B. Keimer. 2004-12-16. Helicoidal magnetic order in a clean copper oxide spin chain compound. https://doi.org/10.1103/physrevb.71.140402

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