J. Phys. IV France 114 (2004) 377
1H-NMR study of Mott insulator -(ET) 2Cu2(CN)3 with isotropic triangular latticeY. Shimizu1, 2, 1, K. Miyagawa2, 3, K. Oda2, K. Kanoda2, 3, M. Maesato1 and G. Saito1
1 Division of Chemistry, Graduate School of Science, Kyoto University, Oiwaketyo, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
2 Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3 CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 332-0012, Japan
1H NMR measurement was performed for a single crystal sample of the organic Mott insulator -(ET) 2Cu 2(CN) 3 with a nearly isotropic triangular lattice. The 1H NMR spectra and the spin-lattice relaxation rate, 1/ T1, show no indication of magnetic transition down to 30 mK. However, the line shows a slight but gradual broadening accompanied with only a moderate increase in the spin-lattice relaxation rate, 1/ T1, below 4 K. It suggests a possible change of spin dynamics of the frustrated quantum spins. Key words. Triangular lattice - Mott insulator - spin liquid.
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