Probing theγ−αTransition in Bulk Ce under Pressure: A Direct Investigation by Resonant Inelastic X-Ray Scattering

Abstract

We report on the most complete investigation to date of the -electron properties at the transition in elemental Ce by resonant inelastic x-ray scattering (RIXS). The Ce 2p3d-RIXS spectra were measured directly in the bulk material as a function of pressure through the transition. The spectra were simulated within the Anderson impurity model. The occupation number n(f) and f double occupancy were derived from the calculations in both gamma and alpha phases in the ground state. We find that the electronic structure changes result mainly from band formation of 4f electrons which concurs with reduced electron correlation and increased Kondo screening at high pressure.

Core and shallow-cored- tof-shell excitations in rare-earth metals

“…The EELS spectra are shown to contain a highly structured, fine mesh of peaks, all perfectly predicted. The NIXS spectra are presented and shown to be in a similarly impressive accord with multiplet theory, for excitations from both the 4d and 3d core shell (the N 4,5 and M 4,5 edges, respectively). However, the electronic excitation structure is a characteristic function of both energy and momentum transfer, so we present comparisons of the momentum transfer dependence as well.…”

“…Resonant and nonresonant x-ray emission spectroscopies have been used to study the lanthanide volume collapse with some success [4,5,20]. However, recent work has shown the value of two other, related inelastic scattering techniques for f-electron interrogation of rare earth materials-nonresonant inelastic x-ray scattering (NIXS) and electron energy loss spectroscopy (EELS) [21][22][23][24][25][26].…”

“…Not coincidentally, these applications often critically depend on the novel properties of the rare earth 4f electrons, properties that are derived primarily from their anisotropic spatial profile and ability to transform between localized and itinerant behavior. The mechanism responsible for 4f electron delocalization is contested [1][2][3][4][5][6][7] However, the borderline between atomic and collective behavior in rare earth metals is often thin, even nearby these seemingly simple cases. Alloying (chemical substitution), pressure, and temperature can effectively tune the 4f electron localization, turning the eigenstates of the system into admixtures of atomic-like states with corresponding admixtures of f-electron occupancy.…”

High-pressure studies with x-rays using diamond anvil cells

“…3). Bassett et al [53,54] drilled holes or grooves on the diamonds to reduce the optical path through them down to several hundred microns, thus greatly reducing the diamond absorption between 5 and 10 keV and enabling HP x-ray spectroscopy of transition element Kedges (e.g., Mn [55] and Fe [56]) and rare-earth element L-edges (e.g., Ce [57,58]). Perforated and partially perforated anvils have been commercially available and widely used for either reducing the diamond absorption [59] or minimizing the background scattering signals from the anvils [60,61].…”

“…NRIXS measurements were first carried out on 57 Fe in its bcc iron at ambient conditions [295,296]. The NRIXS technique has been extended to HP and obtained the DOS of ε-Fe up to over 1 Mbar [63,154] and as a function of pressure and temperature with resistively heating and laser-heating techniques [137,297,298].…”