Spin polarization of the magnetic spiral in NaCu2O2 as seen by nuclear magnetic resonance spectroscopy

The incommensurate (IC) spin ordering in quasi-one-dimensional edge-shared cuprate NaCu2O2 has been studied by Na-23 nuclear magnetic resonance spectroscopy in an external magnetic field near 6 T applied along the main crystallographic axes. The NMR line shape evolution above and below TN approximate to 12 K yields a clear signature of an IC static modulation of the local magnetic field consistent with a Cu2+ spin spiral polarized in the bc plane rather than in the ab plane, as reported from earlier neutron diffraction data.