Europhys. Lett.
Volume 73, Number 1, January 2006
Page(s) 83 - 89
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 02 December 2005
Europhys. Lett., 73 (1), pp. 83-89 (2006)
DOI: 10.1209/epl/i2005-10356-y

Helical ground state and weak ferromagnetism in the edge-shared chain cuprate $\chem{NaCu_2O_2}$

S.-L. Drechsler1, J. Richter2, A. A. Gippius3, A. Vasiliev3, A. A. Bush4, A. S. Moskvin5, J. Málek6, Yu. Prots7, W. Schnelle7 and H. Rosner7

1  IFW Dresden - P.O. Box 270116, D-01171 Dresden, Germany
2  Institut für Theoretische Physik, O.-v.-Guericke-Universität Magdeburg - Germany
3  Moscow State University - Russia
4  Moscow Institute of Radiotechnics, Electronics and Automation - Russia
5  Ural State University - Ekaterinburg, Russia
6  Institute of Physics ASCR - Prague, Czech Republic
7  Max-Planck-Institut für Chemische Physik fester Stoffe - Dresden, Germany

received 15 September 2005; accepted 26 October 2005
published online 2 December 2005

We report on susceptibility, magnetization, $\chem{^{23}Na}$ NMR, and specific heat data of the spin-chain material $\chem{NaCu_2O_2}$ in the paramagnetic and ordered phases. Below 13 K, where a sharp field-dependent specific heat peak appears, the NMR lineshape points to an incommensurate static modulation of the local magnetic field consistent with a spiral state of the Cu magnetic moments. At 2 K weak ferromagnetism with an ordered moment of about 4 $\cdot 10^{-3}\mu_{\rm B}$ has been observed. LDA-based estimates of exchange integrals reveal a large inchain frustration leading to a magnetic spiral.

74.72.Jt - Other cuprates, including Tl and Hg-based cuprates.
76.60.-k - Nuclear magnetic resonance and relaxation.
75.10.Pq - Spin chain models.

© EDP Sciences 2005