Elastic-constant anomalies inYbPO4

Dynamic coupling of crystal-field and phonon states inYbPO4

“…Therefore, these scans permit a comparison of the data with the calculated intensity obtained from a single-ion CF model. Using the CF parameters ͑in units of cm Ϫ1 and the convention of the sphericaltensor formalism, 26 B 0 2 ϭ333, B 0 4 ϭϪ171, B 4 4 ϭϪ641, B 0 6 ϭ Ϫ615, and B 4 6 ϭ175) derived independently from a previous neutron experiment, 21 we find very good agreement between the observed anisotropic intensities and the calculations. For example, at Tϭ100 K the ratios of the observed intensities between the ͑0, 0, 4͒ and ͑4.1, 0, 0͒ scans ͑Fig.…”

“…First, any further splitting of the Kramers doublets would require the breaking of time-reversal symmetry, such as from an electromagnetic field, rather than by local or global structural distortions. Indeed, at zero energy transfer, the elastic line corresponding to the transition within the ⌫ 6 ground doublet observed from both the polycrystalline 21 and single-crystal experiment shows negligible broadening. Therefore, the severe broadening and indications of splitting in the excitations of the ground-to-upper Kramers doublets ͑Figs.…”

“…The outstanding features that are not understood include: ͑i͒ the unusually large coupling strength ͓an order of magnitude larger than those of previously reported systems such as CeAl 2 , 16 PrF 3 , 17 LiTbF 4 , 18 PrAlO 3 , 19 and R(OH) 3 ͑RϭNd, Gd, and Tb͒ 20 ͔, ͑ii͒ the asymmetric linewidths, and ͑iii͒ the wide range of temperatures involved. Nipko et al 21 reported an ϳ20% softening of the (C 11 ϪC 12 )/2 elastic constant with decreasing temperature from 300 to 10 K but no structural phase transition occurred. The CF excitation spectra obtained from neutron time-of-flight spectroscopy using polycrystalline samples revealed broad and asymmetric CF peaks down to 10 K. The relative intensities of these CF transitions cannot be explained quantitatively by a single-ion CF model.…”

“…The ground multiplet 2 F 7/2 of Yb 3ϩ ions in YbPO 4 is split into four Kramers doublets ⌫ 6 , ⌫ 7 , ⌫ 6 , and ⌫ 7 at 0, 12, 32, and ϳ43 meV, respectively. 21 They overlap with the acoustic and the first six optic phonon branches which comprise the substantial motion of the Yb ions. We have measured a majority of these phonon branches as well as the CF transitions along the ͓x, 0 0͔, ͓x, x, 0͔, and ͓0, 0, x͔ symmetry directions at 20 and 295 K. Additional data were taken at 100, 180, and 475 K in order to examine the temperature dependence of the CF-phonon excitations.…”

Compressibility and Phase Transition Kinetics of Lanthanide‐Doped Zircon

“…T he crystal‐chemical, thermodynamic, and physical properties of zircon‐structured compounds (general formula ABO 4 , space group I 4 1 /amd , Z =4) are subject of a wide range of studies in the earth sciences, 1–7 radioactive waste related research, 8–11 and materials science 12–15 . Natural zircon (ZrSiO 4 ) is a common mineral in Earth's crust, and its ability to resist physical and chemical alteration places it among the most commonly used minerals to date geological events 5 .…”