Magnetic spectral response and lattice properties in mixed-valence Sm1-x Yx S solid solutions studied with x-ray diffraction, x-ray absorption spectroscopy, and inelastic neutron scattering

P. A. Alekseev, J. M. Mignot, E. V. Nefeodova, K. S. Nemkovski, V. N. Lazukov, N. N. Tiden, A. P. Menushenkov, R. V. Chernikov, K. V. Klementiev, A. Ochiai, A. V. Golubkov, R. I. Bewley, A. V. Rybina, I. P. Sadikov

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22 Citations (Scopus)

Abstract

Mixed-valence phenomena occurring in the "black" (B) and "gold" (G) phases of Sm1-x Yx S have been studied by x-ray diffraction, x-ray absorption spectroscopy, and inelastic neutron scattering. Lattice-constant and phonon-dispersion results confirm that the valence instability occurs already inside the B phase. On the other hand, pronounced temperature anomalies in the thermal expansion α(T), as well as in the Sm mean-square displacements, denote the onset of the B-G transition for the compositions x=0.33 and 0.45. It is argued that these anomalies primarily denote an effect of electron-phonon coupling. The magnetic spectral response, measured on both powder and single crystals, is dominated by the Sm2+ spin-orbit component close to 36 meV. A strongly overdamped Sm3+ contribution appears only for ≥0.33 near room temperature. The quasielastic signal is strongly suppressed below 70 K, reflecting the formation of the singlet mixed-valence ground state. Quite remarkably, the signal around 36 meV is found, from the single-crystal spectra, to arise from two distinct, dispersive, interacting branches. The lower peak, confirmed to exist from x=0.17 to x=0.33 at least, is tentatively ascribed to an excitation specific to the mixed-valence regime, reminiscent of the "exciton" peak reported previously for SmB6.

Original languageEnglish
Article number035114
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume74
Issue number3
DOIs
Publication statusPublished - 2006
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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