NMR study of the doped chain compounds

D. Arčon; A. Zorko; A. Lappas

doi:10.1209/epl/i2003-10050-2

All issues

Volume 65 / No 1 (January 2004)

Europhys. Lett., 65 1 (2004) 109-115

Abstract

Issue		Europhys. Lett. Volume 65, Number 1, January 2004


Page(s)		109 - 115
Section		Condensed matter: electronic structure, electrical, magnetic, and optical properties
DOI		https://doi.org/10.1209/epl/i2003-10050-2
Published online		01 December 2003

Europhys. Lett., 65 (1), pp. 109-115 (2004)

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

D. Arčon¹^,2, A. Zorko¹ and A. Lappas³

¹ 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

Received: 28 July 2003
Accepted: 23 October 2003

Abstract

$\chem{{}^{51}V}$ 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.

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

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