Abstract
Using neutron diffraction, Mössbauer and muon spin relaxation spectroscopies, we have examined the pyrochlore , where the ground state has planar anisotropy. Below , the temperature of the known specific-heat transition, there is no long range magnetic order. We show that the transition corresponds to a first-order change in the fluctuation rate of the spins. Above the transition temperature, the rate, in the GHz range, follows a thermal excitation law, whereas below, the rate, in the MHz range, is temperature independent, indicative of a quantum fluctuation regime.
- Received 4 September 2001
DOI:https://doi.org/10.1103/PhysRevLett.88.077204
©2002 American Physical Society