The SrCr_9pGa_12−9pO_19 and Ba_2Sn_2ZnGa_10−7pCr_7pO_22 compounds are two highly-frustrated magnets possessing a quasi-two-dimensional Kagom\'{e} bilayer of spin 3/2 chromium ions with antiferromagnetic interactions. Their magnetic susceptibility was measured by local Nuclear Magnetic Resonance and non-local (SQUID) techniques, and their low-temperature spin dynamics by Muon Spin Resonance. Consistent with the theoretical picture drawn for geometrically frustrated systems, the Kagom\'{e} bilayer is shown here to exhibit: (i) short range spin-spin correlations down to a temperature much lower than the Curie-Weiss temperature, no conventional long-range transition occurring; (ii) a Curie contribution to the susceptibility from paramagnetic defects generated by spin vacancies; (iii) low-temperature spin fluctuations, at least down to 30 mK, which are a trademark of a dynamical ground state. These properties point to a spin-liquid ground state, possibly built on Resonating Valence Bonds with unconfined spinons as the magnetic excitations.
@article{arxiv.cond-mat/0503496,
title = {Correlations, spin dynamics, defects: the highly-frustrated Kagom\'{e} bilayer},
author = {David Bono and Laurent Limot and Philippe Mendels and Gaston Collin and Nicole Blanchard},
journal= {arXiv preprint arXiv:cond-mat/0503496},
year = {2007}
}