Universal geometric frustration in pyrochlores.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29976983.
- Also identified by DOI 10.1038/s41467-018-05033-7 and PMC identifier 6033937.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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 A<sub>2</sub>Zr<sub>2</sub>O<sub>6</sub>O' (A = Pr, La) and Yb<sub>2</sub>Ti<sub>2</sub>O<sub>6</sub>O', 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 A<sub>2</sub>O' 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.