Universal geometric frustration in pyrochlores
B A Trump1,2,3, S M Koohpayeh3, K J T Livi4
1NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
Nature Communications
|July 7, 2018
Summary
Structural instability was found in pyrochlore materials, even with ideal stoichiometry. Local structure probes revealed atomic displacements, mimicking fluxional motions in silica, impacting quantum spin ices and ferroelectric properties.
Area of Science:
- Materials Science
- Solid State Chemistry
- Crystallography
Background:
- Pyrochlore and fluorite structures are vital for applications including magnetism and nuclear waste management.
- These materials exhibit diverse technological uses, underscoring the importance of understanding their structural properties.
Purpose of the Study:
- To investigate structural instability in pyrochlores (A₂Zr₂O₆O' and Yb₂Ti₂O₆O') despite ideal stoichiometry and cation ordering.
- To characterize local atomic displacements within the pyrochlore framework and their implications.
Main Methods:
- Local structure probes were employed to detect atomic displacements.
- Comparison of observed displacement patterns with known fluxional motions in materials like β-cristobalite.
Main Results:
- Structural instability was observed in A₂Zr₂O₆O' (A=Pr, La) and Yb₂Ti₂O₆O' pyrochlores.
- Atomic displacements of approximately 0.01 nm were detected within the pyrochlore framework.
- The observed displacements resemble the fluxional motions found in silica mineral β-cristobalite.
Conclusions:
- The study reveals inherent structural instability in certain pyrochlores, independent of stoichiometry or magnetic order.
- These fluxional displacements contribute to the structural diversity of pyrochlores.
- The findings explain the sensitivity of quantum spin ices to composition and the absence of ferroelectricity in these pyrochlores.
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