TY - JOUR
T1 - 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
AU - Alekseev, P. A.
AU - Mignot, J. M.
AU - Nefeodova, E. V.
AU - Nemkovski, K. S.
AU - Lazukov, V. N.
AU - Tiden, N. N.
AU - Menushenkov, A. P.
AU - Chernikov, R. V.
AU - Klementiev, K. V.
AU - Ochiai, A.
AU - Golubkov, A. V.
AU - Bewley, R. I.
AU - Rybina, A. V.
AU - Sadikov, I. P.
PY - 2006
Y1 - 2006
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevB.74.035114
DO - 10.1103/PhysRevB.74.035114
M3 - Article
AN - SCOPUS:33746255879
VL - 74
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
SN - 0163-1829
IS - 3
M1 - 035114
ER -