Spin Ice: Magnetic Excitations without Monopole Signatures Using Muon Spin Rotation

S. R. Dunsiger, A. A. Aczel, C. Arguello, H. Dabkowska, A. Dabkowski, M.-H. Du, T. Goko, B. Javanparast, T. Lin, F. L. Ning, H. M. L. Noad, D. J. Singh, T. J. Williams, Y. J. Uemura, M. J. P. Gingras, and G. M. Luke

Phys. Rev. Lett. 107, 207207 – Published 11 November 2011

Abstract

Theory predicts the low temperature magnetic excitations in spin ices consist of deconfined magnetic charges, or monopoles. A recent transverse-field (TF) muon spin rotation ( $μ SR$ ) experiment [S. T. Bramwell et al., Nature (London) 461, 956 (2009)] reports results claiming to be consistent with the temperature and magnetic field dependence anticipated for monopole nucleation—the so-called second Wien effect. We demonstrate via a new series of $μ SR$ experiments in ${Dy}_{2} {Ti}_{2} O_{7}$ that such an effect is not observable in a TF $μ SR$ experiment. Rather, as found in many highly frustrated magnetic materials, we observe spin fluctuations which become temperature independent at low temperatures, behavior which dominates over any possible signature of thermally nucleated monopole excitations.

Received 4 August 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.207207

Authors & Affiliations

S. R. Dunsiger^1,*, A. A. Aczel², C. Arguello³, H. Dabkowska⁴, A. Dabkowski⁴, M.-H. Du⁵, T. Goko^3,6, B. Javanparast⁷, T. Lin⁷, F. L. Ning^3,8, H. M. L. Noad², D. J. Singh⁵, T. J. Williams², Y. J. Uemura^3,†, M. J. P. Gingras^7,9,‡, and G. M. Luke^2,9,§

¹Physik Department, Technische Universität München, D-85748 Garching, Germany
²Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
³Department of Physics, Columbia University, New York, New York 10027, USA
⁴Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada
⁵Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6114, USA
⁶TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
⁷Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
⁸Department of Physics, Zhejiang University, Hangzhou 310027, China
⁹Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada