First-order transition in the spin dynamics of geometrically frustrated Yb2Ti2O7 |
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Authors: | Hodges J A Bonville P Forget A Yaouanc A Dalmas de Réotier P André G Rams M Królas K Ritter C Gubbens P C M Kaiser C T King P J C Baines C |
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Institution: | CEA-Saclay, DRECAM-SPEC, 91191 Gif-sur-Yvette, France. |
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Abstract: | Using neutron diffraction, 170Yb M?ssbauer and muon spin relaxation spectroscopies, we have examined the pyrochlore Yb2Ti2O7, where the Yb3+S' = 1/2 ground state has planar anisotropy. Below approximately 0.24 K, the temperature of the known specific-heat lambda 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 Yb3+ 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. |
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