Europhys. Lett.
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
Europhys. Lett., 65 (1) , pp. 109-115 (2004)
DOI: 10.1209/epl/i2003-10050-2

$\chem{{}^{51}V}$ NMR study of the doped chain compounds $\chem{PbNi}$ 2-x $\chem{Mg}$ x $\chem{V_{2}O_{8}}$

D. Arcon1, 2, A. Zorko1 and A. Lappas3

1  Institute "Jozef 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

(Received 28 July 2003; accepted in final form 23 October 2003)

$\chem{{}^{51}V}$ NMR has been measured in polycrystalline chain compounds $\chem{PbNi}$ 2-x $\chem{Mg}$ x $\chem{V_{2}O_{8}}$ ( x = 0, 0.12, 0.24 ) between room temperature and 4 $\un{K}$. A broad strongly shifted resonance has been found in all three cases, suggesting that $\chem{VO_{4}}$ tetrahedra serve as a superexchange bridge between $\chem{Ni^{2+}}$ chains. The temperature dependence of the first moment of the $\chem{{}^{51}V}$ 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 $\chem{{}^{51}V}$ NMR spectra and the spin-lattice relaxation data suggest that short-range antiferromagnetic correlations already develop at $T\leq 100$ $\un{K}$ and coexist with the 1D magnetic excitations in the $\chem{Mg}$-substituted derivatives. In addition, we propose that not all $\chem{{}^{51}V}$ NMR centres remain equivalent after doping. Namely, in $\chem{Mg}$-doped samples we find an intense, narrow $\chem{{}^{51}V}$ NMR line whose origin is compatible with the deformed $\chem{VO_{4}}$ tetrahedra.

75.50.Ee - Antiferromagnetics.
75.10.Jm - Quantized spin models.
76.60.-k - Nuclear magnetic resonance and relaxation.

© EDP Sciences 2004