Abstract
The family of layered organic salts are Mott insulators and form scalene-triangular spin- systems. Among them, has a nearly regular-triangular lattice. We have investigated the spin state of this salt by and static susceptibility measurements. The temperature dependence of the susceptibility is described as that of a regular-triangular antiferromagnetic spin- system with an exchange interaction . The measurements reveal that there is no indication of either spin ordering/freezing or an appreciable spin gap down to , which is lower than 1% of . This result strongly suggests that this system is in the quantum spin-liquid state with no appreciable spin gap, which has been long sought after.
- Received 1 August 2007
DOI:https://doi.org/10.1103/PhysRevB.77.104413
©2008 American Physical Society