Sample independence of magnetoelastic excitations in the rare-earth pyrochloreTb2Ti2O7

Abstract

Recent experimental results have emphasized two aspects of Tb2Ti2O7 which have not been taken into account in previous attempts to construct theories of Tb2Ti2O7: the role of small levels of structural disorder, which appears to control the formation of a long-range ordered state of as yet unknown nature; and the importance of strong coupling between spin and lattice degrees of freedom, which results in the hybridization of crystal field excitons and transverse acoustic phonons. In this work we examine the juncture of these two phenomena and show that samples with strongly contrasting behavior vis-a-vis the structural disorder (i.e. with and without the transition to the ordered state), develop identical magnetoelastic coupling. We also show that the comparison between single crystal and powder samples is more complicated than previously thought -the correlation between lattice parameter (as a measure of superstoichiometric Tb 3+ ) and the existence of a specific heat peak, as observed in powder samples, does not hold for single crystals. arXiv:1510.07572v2 [cond-mat.str-el]

First-principles calculation and experimental investigation of lattice dynamics in the rare-earth pyrochloresR2Ti2O7(R=Ruminy1, Valdez2, Wehinger3 et al. 2016Phys. Rev. BSelf Cite336480View full textAdd to dashboardCite

“…Particularly interesting with respect to the frustrated [7] (Supplemental Material)] and discussed further in Ref. [49], with the lattice contribution derived from the density functional calculations presented here. We suggest that DFT calculations could provide a means to accurately estimate the lattice contribution to such measurements.…”

“…The Tb 2 Ti 2 O 7 sample was a large single crystal of mass ≈7 g, grown in a floating zone furnace. It has been previously used to investigate diffuse and inelastic neutron scattering [7,48], and characterized extensively [7,49]. The crystals were both aligned with the [110] direction vertical, to give an (h,h,l) scattering plane.…”

Neutron Larmor diffraction investigation of the rare-earth pyrochlores R2Ti2O7 ( R=Tb , Dy, Ho

“…Its characterization by x-ray diffraction and specific heat measurements have been discussed in Refs. [12] and [23] (it does not have the specific heat peak found in some Tb 2 Ti 2 O 7 samples [24,25]). The Dy 2 Ti 2 O 7 crystal [26] is somewhat smaller ( 1.5 g) because it is isotopically enriched with 162 Dy to reduce the large absorption cross section of natural isotopic abundance dysprosium.…”

“…6 for Dy 2 Ti 2 O 7 , and the relevant values of the lattice parameters are given in Table I. We have also recently determined the room temperature lattice parameters of each compound by synchrotron powder x-ray diffraction with calibration against a NIST silicon standard [23,32]. Those lattice parameters are also shown in the table, O 7 , which has a sample dependent lattice parameter, is from a fragment of the same crystal (which is known as MH1 in Ref.…”

“…Those lattice parameters are also shown in the table, O 7 , which has a sample dependent lattice parameter, is from a fragment of the same crystal (which is known as MH1 in Ref. [23])).…”