Volume 65, Number 1, January 2004
|Page(s)||109 - 115|
|Section||Condensed matter: electronic structure, electrical, magnetic, and optical properties|
|Published online||01 December 2003|
NMR study of the doped chain compounds
Institute “Jožef Stefan” - Jamova 39, 1000 Ljubljana, Slovenia
2 Faculty of Mathematics and Physics, University of Ljubljana Jadranska 19, 1000 Ljubljana, Slovenia
3 Institute of Electronic Structure & Laser Foundation for Research & Technology-Hellas P.O. Box 1527, 711 10 Heraklion, Crete, Greece
Accepted: 23 October 2003
NMR has been measured in polycrystalline chain compounds x () between room temperature and 4. A broad strongly shifted resonance has been found in all three cases, suggesting that tetrahedra serve as a superexchange bridge between chains. The temperature dependence of the first moment of the NMR lines demonstrates the existence of a spin-gap down to very low temperatures even in doped samples. On the other hand, the large inhomogeneous broadening of the NMR spectra and the spin-lattice relaxation data suggest that short-range antiferromagnetic correlations already develop at and coexist with the 1D magnetic excitations in the -substituted derivatives. In addition, we propose that not all NMR centres remain equivalent after doping. Namely, in -doped samples we find an intense, narrow NMR line whose origin is compatible with the deformed tetrahedra.
PACS: 75.50.Ee – Antiferromagnetics / 75.10.Jm – Quantized spin models / 76.60.-k – Nuclear magnetic resonance and relaxation
© EDP Sciences, 2004
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