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

S.-L. Drechsler; J. Richter; A. A. Gippius; A. Vasiliev; A. A. Bush; A. S. Moskvin; J. Málek; Yu. Prots; W. Schnelle; H. Rosner

doi:doi:10.1209/epl/i2005-10356-y

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

drechsler@ifw-dresden.de

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

Abstract
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.

PACS
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