College Park, Maryland June 6 - 10 , 2004
W2-D1 (1:30 PM): Spin Echo Study of the Dynamics of Spin Ice (Invited)
G. Ehlers (Spallation Neutron Source, Oak Ridge National Laboratory), J. S. Gardner (Physics Department, Brookhaven National Laboratory; NIST Center for Neutron Research), N. Rosov (NIST Center for Neutron Research), W. Häussler (Institut Laue Langevin), S. T. Bramwell, J. Lago (Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK)
Neutron spin echo measurements have been performed at NIST and at ILL on the spin ice related materials Ho2-xYxTi2O7 (0≤x≤1.8) to study the spin relaxation processes in the paramagnetic phase (T>1K) . A cross-over from a thermally activated single-ion process to a temperature independent quantum mechanical process occurs at T ≈15K in samples with moderate magnetic dilution (x≤1.1). However in very dilute samples x ≥1.6 another, faster relaxation process appears at relatively high temperature (up to at least T≈55K). Our neutron data will be discussed in relation to complementary a.c. susceptibility and μSR results.
 G. Ehlers, A. L. Cornelius, M. Orendac, M. Krajnakova, T. Fennell, S. T. Bramwell, and J. S. Gardner, J Phys: Condens. Matter 15, L9 (2003).
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