Structural properties of the geometrically frustrated pyrochlore Tb2Ti2O7
Although materials that exhibit nearest-neighbor-only antiferromagnetic interactions and geometrical frustration theoretically should not magnetically order in the absence of disorder, few such systems have been observed experimentally. One such system appears to be the pyrochlore Tb{sub 2}Ti{sub 2}O{sub 7}. However, previous structural studies indicated that Tb{sub 2}Ti{sub 2}O{sub 7} is an imperfect pyrochlore. To clarify the situation, we performed neutron powder diffraction (NPD) and x-ray absorption fine structure (XAFS) measurements on samples that were prepared identically to those that show no magnetic order. The NPD measurements show that the long-range structure of Tb{sub 2}Ti{sub 2}O{sub 7} is well ordered with no structural transitions between 4.5 and 600 K. In particular, mean-squared displacements (u{sup 2}'s) for each site follow a Debye model with no offsets. No evidence for Tb/Ti site interchange was observed within an upper limit of 2%. Likewise, no excess or deficiency in the oxygen stoichiometry was observed, within an upper limit of 2% of the nominal pyrochlore value. Tb L{sub III} and Ti K-edge XAFS measurements from 20-300 K similarly indicate a well-ordered local structure. Other aspects of the structure are considered. We conclude that Tb{sub 2}Ti{sub 2}O{sub 7} has, within experimental error, an ideal, disorder-free pyrochlore lattice, thereby allowing the system to remain in a dynamic, frustrated spin state to the lowest observed temperatures.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science Contract DE-AC03-76SF00098, Office of Basic Energy Sciences. Materials Sciences Division. Brookhaven National Laboratory Contract DE-AC02-98CH10886, Argonne National Laboratory Contract W-31-109-ENG-38, Stanford University
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 842967
- Report Number(s):
- LBNL-54103; R&D Project: 365723; TRN: US0503786
- Resource Relation:
- Other Information: Journal Publication Date: 2004
- Country of Publication:
- United States
- Language:
- English
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