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Quenching of the Haldane gap in LiVSi2O6 and related compounds

B. Pedrini·S. Wessel·J. L. Gavilano·H. R. Ott·S. M. Kazakov·J. Karpinski
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Abstract

We report results of susceptibility chi and 7Li NMR measurements on LiVSi2O6. The temperature dependence of the magnetic susceptibility chi(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 LiVSi2O6, and also for its sister compounds LiVGe2O6, NaVSi2O6 and NaVGe2O6, 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.

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B. Pedrini, S. Wessel, J. L. Gavilano, H. R. Ott, S. M. Kazakov, J. Karpinski. 2006-06-06. Quenching of the Haldane gap in LiVSi2O6 and related compounds. https://doi.org/10.1140/epjb%2Fe2007-00056-0

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