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Dipolar magnets and glasses: Neutron-scattering, dynamical, and calorimetric studies of randomly distributed Ising spins

Reich, D. H. and Ellman, B. and Yang, J. and Rosenbaum, T. F. and Aeppli, G. and Belanger, D. P. (1990) Dipolar magnets and glasses: Neutron-scattering, dynamical, and calorimetric studies of randomly distributed Ising spins. Physical Review B, 42 (7). pp. 4631-4644. ISSN 1098-0121. https://resolver.caltech.edu/CaltechAUTHORS:20140707-163038991

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Abstract

We have measured the magnetic correlations, susceptibility, specific heat, and thermal relaxation in the dipolar-coupled Ising system LiHo_xY_(1-x)F_4. The material is ferromagnetic for spin concentrations at least as low as x=0.46, with a Curie temperature obeying mean-field scaling relative to that of pure LiHoF_4. In contrast, an x=0.167 sample behaves as a spin glass above its transition temperature, while an x=0.045 crystal shows very different glassy properties characterized by decreasing barriers to relaxation and nonexponential thermal relaxation as T→0. We find the properties of the x=0.045 system to be consistent with a single low-degeneracy ground state with a large gap for excitations. The x=0.167 sample, however, supports a complex ground state with no appreciable gap, in accordance with prevailing theories of spin glasses. The underlying causes of such disparate behavior are discussed in terms of random clusters as probed by neutron studies of the x=0.167 sample.


Item Type:Article
Related URLs:
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http://dx.doi.org/10.1103/PhysRevB.42.4631DOIArticle
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.42.4631PublisherArticle
Additional Information:© 1990 The American Physical Society. Received 23 April 1990. The work at The University of Chicago was supported by the National Science Foundation (NSF) Materials Research Laboratory under Grant No. 88-19860. We are grateful to S. R. Nagel, D. L. Stein, and C. Yu for helpful discussions. We thank S. Shapiro and J. Axe for their generous hospitality at Brookhaven National Laboratory (BNL). Neutron scattering at BNL was supported by the Division of Materials Science, U.S. Department of Energy, under Contract No. DE-AC02-76CH0016. D. H. Reich submits this paper in partial fulfillment of the requirements for the Ph.D. degree at The University of Chicago. Thanks are also due to the Aspen Center for Physics, where part of the work leading to this paper was done.
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Funding AgencyGrant Number
NSF88-19860
Department of Energy (DOE)DE-AC02-76CH0016
Issue or Number:7
Record Number:CaltechAUTHORS:20140707-163038991
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140707-163038991
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47025
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:09 Jul 2014 17:03
Last Modified:03 Oct 2019 06:48

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