Correlations, spin dynamics, defects: the highly frustrated kagomé bilayer

The compounds SrCr 9p Ga 12−9p O 19 and Ba 2 Sn 2 ZnGa 10−7p Cr 7p O 22 are two highly frustrated magnets possessing a quasi-two-dimensional kagomé bilayer of spin-3/2 chromium ions with antiferromagnetic interactions. Their magnetic susceptibility was measured by local nuclear magnetic resonance an...

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Bibliographic Details
Published in:Low temperature physics (Woodbury, N.Y.) N.Y.), 2005-08, Vol.31 (8), p.704-721
Main Authors: Bono, D., Limot, L., Mendels, P., Collin, G., Blanchard, N.
Format: Article
Language:English
Subjects:
Condensed Matter
Physics
Strongly Correlated Electrons
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Summary:The compounds SrCr 9p Ga 12−9p O 19 and Ba 2 Sn 2 ZnGa 10−7p Cr 7p O 22 are two highly frustrated magnets possessing a quasi-two-dimensional kagomé bilayer of spin-3/2 chromium ions with antiferromagnetic interactions. Their magnetic susceptibility was measured by local nuclear magnetic resonance and nonlocal (SQUID) techniques, and their low-temperature spin dynamics by muon spin resonance. Consistent with the theoretical picture drawn for geometrically frustrated systems, the kagomé 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.
ISSN:1063-777X
1090-6517
DOI:10.1063/1.2008131