Mapping out a quantum spin liquid

Diagrams representing the spin liquid phase

The ordering expected for a triangular lattice S=1/2 Heisenberg antiferromagnet (background). Left: the κ−(ET)2Cu2(CN)3 spin liquid. Right: field-induced recovery of its suppressed magnetism.
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Muons are used to probe the magnetic properties of a phase that is of great interest to physicists.

In magnetism, the idea of a quantum spin liquid phase has fascinated theoretical and experimental physicists for many decades. In such a phase, the ordered magnetic state, as usually found in systems of interacting magnetic spins, is completely absent due to the destabilising effect of strong quantum fluctuations.

Although the idea of the spin liquid is quite old, it is only recently that experimental systems have become available that show all the hallmarks of such a state. This is particularly the case in materials containing triangular lattices of spin-1/2 molecular radical dimers. One such system, κ-(ET)2Cu(CN)3, has been the focus of intense study since its discovery a few years ago.

Muons provide an exquisitely sensitive local probe of magnetic properties. Recent muon experiments at ISIS show that a weak magnetic phase can be recovered from the spin-liquid phase using a very small magnetic field.

FL Pratt, PJ Baker (ISIS), SJ Blundell, T Lancaster (Oxford),
S Ohira-Kawamura (J-PARC), C Baines (PSI), Y Shimizu (Nagoya), K Kanoda (Tokyo), I Watanabe (RIKEN), G Saito (Kyoto)

Research date: August 2011

Further Information

Contact: Dr FL Pratt, francis.pratt@stfc.ac.uk
Further reading: FL Pratt et al., Nature 471 (2011) 612

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