Dynamic coupling of crystal-field and phonon states inYbPO4

Abstract

The dynamic response of 4 f -electron-lattice interactions in YbPO 4 was characterized by neutron spectroscopy using single-crystal specimens. The Yb 3ϩ : 2 F 7/2 ground multiplet shows broadened and overdamped energy levels. A coupling of the upper ⌫ 6 and ⌫ 7 states with optic phonons was observed throughout the Brillouin zone, resulting in a strong renormalization of the bare crystal-field and phonon excitation spectra over the 15 to 475 K temperature range. A mechanism involving monopolar fluctuations of the Yb f orbital is proposed.

Low-temperature Raman spectra of YbVO4

“…No evidence either for electron-phonon coupling or JT structural phase transition is observed. We tentatively explain these results using the values obtained from the CF model for YbVO 4 [14] and YbPO 4 [13].…”

“…[21,13], respectively. In particular, the ground-state multiplet of Yb 3+ in YbPO 4 is split into four Kramers doublets G 6 , G 7 , G 6 , and G 7 at 0, 96.8, 258 and $347 cm À1 , respectively, as observed by magnetic inelastic neutron scattering (INS) at 15K where the CF-phonon effect on the energies of the CF states is thought to be minimum.…”

“…On cooling down to 4.2 K, its linewidth does not narrow as usually expected, but, instead, it splits into two sharp wings (249 and 345 cm À1 ) plus a broad central feature ($298 cm À1 ), spanning a central region of almost 100 cm À1 . These features were explained as resulting from the mixing of two Yb 3+ crystal field (CF) states with the E 3 g phonon mode from 4.2 to 300 K. The wavevector-dependence of these phonon branches was studied further subsequently by Loong et al [13] through neutron spectroscopy.…”

Inelastic neutron scattering, lattice dynamics, and high-pressure phase stability of zircon-structured lanthanide orthophosphates

“…The excellent refractory properties at high temperatures, high radiation-damage resistance, and good chemical stabilities have prompted systematic investigations by many workers. 5 These include studies of optical, 6 transport, 7 phonon, 8,9 and thermochemical properties, [10][11][12] the variation in thermal and mechanical properties with respect to the rareearth constitutions 13,14 and radiation effects 15,16 by various theoretical and experimental techniques. [17][18][19][20] However, we are not aware of a systematic assessment of the phonon spectra and the associated thermodynamic properties and possible phase transformations in the heavy lanthanide orthophosphates.…”

Magnetic properties and signatures of moment ordering in triangular lattice antiferromagnet KCeO$_2$

“…This considerably weakens the possibility that the extra mode at 170 meV arises from a transition into a J = 7/2 state. Anomalous CEF modes observed for lanthanide ions in similar crystallographic environments are often explained by invoking coupling to phonons or vibronic effects [66][67][68][69][70][71][72], conjectures of hydrogen embedded within the sample [73][74][75][76][77][78][79], or the potential presence of chemical impurities creating…”