First-order transition in the spin dynamics of geometrically frustrated Yb2Ti2O7.
Using neutron diffraction, 170Yb Mössbauer 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.
Hodges
J A
JA
CEA-Saclay, DRECAM-SPEC, 91191 Gif-sur-Yvette, France.
Bonville
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P
Forget
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Yaouanc
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A
Dalmas de Réotier
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P
André
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G
Rams
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M
Królas
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K
Ritter
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Gubbens
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Kaiser
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King
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PJ
Baines
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C