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Spin dynamics of the model 2D quantum antiferromagnet CFTD

H. M. Ronnow, D. F. McMorrow, R. Coldea, A. Harrison, I. D. Youngson, T. G. Perring, G. Aeppli, O. Syljyasen, K. Lefmann, C. Rischel

cond-matarXiv:cond-mat/0101238

Abstract

The magnetic excitation spectrum in the two-dimensional (2D) S=1/2 Heisenberg antiferromagnet copper deuteroformate tetradeuterate (CFTD) has been measured for temperatures up to T J/2, where J=6.31+-0.02 meV is the 2D exchange coupling. For T J, a dispersion of the zone boundary energy is observed, which is attributed to a wavevector dependent quantum renormalization. At higher temperatures, spin-wave-like excitations persist, but are found to broaden and soften. By combining our data with numerical calculations, and with existing theoretical work, a consistent description of the behaviour of the model system is found over the whole temperature interval investigated.

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