A new candidate for spin liquid physics

Phase diagram for the paratacamite family

Phase diagram for the paratacamite family compounds Cu4-xZnx(OH)6Cl2. Magnetic order vanishes as the perfect Kagome case (x=1) is approached.
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In most common magnetic ground states, the moments of atoms in crystals order because of interactions with their neighbours.

However, in triangular lattices three spins can not be simultaneously anti-parallel to each other and therefore cannot satisfy antiferromagnetic interactions. In 1973, Anderson proposed that such magnetic frustration associated with large quantum fluctuations for S = 1/2 spins could stabilize a ‘spin liquid’ ground state built on the resonance of singlets between neighbouring bonds. This concept has been seminal for many theoretical investigations, including high temperature superconductors, but has not yet been realized experimentally. A new synthetic material Cu3Zn(OH)6Cl2, a close relative of a mineral compound discovered in a Chilean mine in 2004 and based on spin triangles forming a Kagomé net, could well be the very first realization of this novel state. Using the high sensitivity of muons, we demonstrated the absence of any magnetic ordering down to a 50 mK, well below the 200 K coupling energy of the spins. This makes Cu3Zn(OH)6Cl2 a very promising candidate for spin liquid physics.

P Mendels, F Bert (Universite Paris- Sud, France), MA de Vries (University of Edinburgh), A Olariu (Universite Paris-Sud, France), A Harrison (ILL, France), F Duc, JC Trombe (CNRS, France), JS Lord (ISIS), A Amato, C Baines (PSI, Switzerland)

Research date: December 2007

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