Structural properties of the geometrically frustrated pyrochlore Tb 2 Ti 2 O 7

摘要: 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 system appears to be pyrochlore ${\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}.$ However, previous structural studies indicated ${\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ is an imperfect pyrochlore. To clarify situation, we performed neutron powder-diffraction (NPD) x-ray absorption fine-structure (XAFS) measurements on samples were prepared identically those show no magnetic order. The NPD long-range structure well ordered with transitions between 4.5 600 K. In particular, mean-squared displacements ${u}^{2}\mathrm{'}\mathrm{s}$ for each site follow a Debye model offsets. No evidence Tb/Ti interchange was within upper limit 2%. Likewise, excess or deficiency oxygen stoichiometry observed, 2% nominal value. Tb ${L}_{\mathrm{III}}$- Ti K-edge XAFS from 20 K 300 similarly indicate well-ordered local structure. Other aspects are considered. We conclude has, experimental error, ideal, disorder-free lattice, thereby allowing remain dynamic, frustrated spin state lowest temperatures.