Quenching of the Haldane gap in LiVSi 2 O 6 and related compounds

B. Pedrini (), S. Wessel, J. L. Gavilano, H. R. Ott, S. M. Kazakov and J. Karpinski

The European Physical Journal B: Condensed Matter and Complex Systems, 2007, vol. 55, issue 3, 219-228

Abstract: We report results of susceptibility χ and 7 Li NMR measurements on LiVSi 2 O 6 . The temperature dependence of the magnetic susceptibility χ(T) exhibits a broad maximum, typical for low-dimensional magnetic systems. Quantitatively it is in agreement with the expectation for an S=1 spin chain, represented by the structural arrangement of V ions. The NMR results indicate antiferromagnetic ordering below T N =24 K. The intra- and interchain coupling J and J p for LiVSi 2 O 6 , and also for its sister compounds LiVGe 2 O 6 , NaVSi 2 O 6 and NaVGe 2 O 6 , are obtained via a modified random phase approximation which takes into account results of quantum Monte Carlo calculations. While J p is almost constant across the series, J varies by a factor of 5, decreasing with increasing lattice constant along the chain direction. The comparison between experimental and theoretical susceptibility data suggests the presence of an easy-axis magnetic anisotropy, which explains the formation of an energy gap in the magnetic excitation spectrum below T N , indicated by the variation of the NMR spin-lattice relaxation rate at T≪T N . Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007

Keywords: 76.60.-k Nuclear magnetic resonance and relaxation; 02.70.Ss Quantum Monte Carlo methods; 75.10.Pq Spin chain models; 75.30.Cr Saturation moments and magnetic susceptibilities (search for similar items in EconPapers)
Date: 2007
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DOI: 10.1140/epjb/e2007-00056-0

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