Universal geometric frustration in pyrochlores

B A Trump; S M Koohpayeh; K J T Livi; J-J Wen; K E Arpino; Q M Ramasse; R Brydson; M Feygenson; H Takeda; M Takigawa; K Kimura; S Nakatsuji; C L Broholm; T M McQueen

doi:10.1038/s41467-018-05033-7

Universal geometric frustration in pyrochlores

Nat Commun. 2018 Jul 5;9(1):2619. doi: 10.1038/s41467-018-05033-7.

Authors

B A Trump^{1

2

3}, S M Koohpayeh³, K J T Livi⁴, J-J Wen³, K E Arpino^{2

3}, Q M Ramasse⁵, R Brydson⁶, M Feygenson⁷, H Takeda⁸, M Takigawa⁸, K Kimura⁹, S Nakatsuji⁸, C L Broholm^{3

4}, T M McQueen^{10

11

12}

Affiliations

¹ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
² Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.
³ Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA.
⁴ Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA.
⁵ SuperSTEM Laboratory, STFC Daresbury Campus, Daresbury, WA4 4AD, UK.
⁶ School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK.
⁷ Jülich Center for Neutron Science, Forschungszentrum Jülich GmbH, D-52425, Jülich, Germany.
⁸ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
⁹ Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
¹⁰ Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA. mcqueen@jhu.edu.
¹¹ Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA. mcqueen@jhu.edu.
¹² Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA. mcqueen@jhu.edu.

Abstract

Materials with the pyrochlore/fluorite structure have diverse technological applications, from magnetism to nuclear waste disposal. Here we report the observation of structural instability present in the pyrochlores A₂Zr₂O₆O' (A = Pr, La) and Yb₂Ti₂O₆O', that exists despite ideal stoichiometry, ideal cation-ordering, the absence of lone pair effects, and a lack of magnetic order. Though these materials appear to have good long-range order, local structure probes find displacements, of the order of 0.01 nm, within the pyrochlore framework. The pattern of displacements of the A₂O' sublattice mimics the entropically-driven fluxional motions characteristic of and well-known in the silica mineral β-cristobalite. The universality of such displacements within the pyrochlore structure adds to the known structural diversity and explains the extreme sensitivity to composition found in quantum spin ices and the lack of ferroelectric behavior in pyrochlores.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.