The nature of the gapped ground state in the quasi-one-dimensional compound eta-Na9V14O35 cannot easily be understood, if one takes into account the odd number of spins on each structural element. Combining the results of specific heat, susceptibility and electron spin resonance measurements we show that eta-Na9V14O35 exhibits a novel ground state where multi-spin objects build up a linear chain. These objects - pentamers - consist of five antiferromagnetically arranged spins with effective spin 1/2. Their spatial extent results in an exchange constant along the chain direction comparable to the one in the high-temperature state.
@article{arxiv.0809.0619,
title = {Chain Formation by Spin Pentamers in eta-Na9V14O35},
author = {D. V. Zakharov and H. -A. Krug von Nidda and J. Deisenhofer and F. Schrettle and G. Obermeier and S. Horn and A. Loidl},
journal= {arXiv preprint arXiv:0809.0619},
year = {2009}
}