α−γtransition in metallicCestudied by resonant x-ray spectroscopies

Abstract

We performed bulk-sensitive x-ray absorption (XAS) in the partial fluorescence yield (PFY) mode, and resonant x-ray emission (RXES) measurements of the solid solution Sc (7 at.%):$\mathrm{Ce}$ at the $\mathrm{Ce}\phantom{\rule{0.3em}{0ex}}{\mathrm{L}}_{3}\phantom{\rule{0.3em}{0ex}}(2p\ensuremath{\rightarrow}5d)$ and ${\mathrm{M}}_{4,5}\phantom{\rule{0.3em}{0ex}}(3d\ensuremath{\rightarrow}4f)$ absorption edges. We deduce an increasing $4f$-band hybridization from the $\ensuremath{\gamma}$-phase stable at room temperature to the low-temperature $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Ce}$, consistent with the ``Kondo collapse'' scenario for the transition. The enhanced intrinsic resolution of $\mathrm{PFY}\text{\ensuremath{-}}\mathrm{XAS}$ allows us to resolve the elusive three-peak structure predicted by theory. Thanks to the selective enhancement typical of RXES, we could estimate the small but non-negligible contribution of the ${f}^{2}$ configuration in the hybrid ground state, and its change in the two phases. The linear dichroism effect in the ${\mathrm{M}}_{4,5}$ RXES spectra is consistent with the observed hybridization of $4f$ and conduction states.