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Published on: November 11, 2013
Valence fluctuations in the 3D + 3 modulated Yb3Co4Ge13 Remeika phase
Manuel Feig1,2, Lev Akselrud2,3, Mykhaylo Motylenko4
1Institut für Experimentelle Physik, TU Bergakademie Freiberg, Leipziger Straße 23, 09596 Freiberg, Germany. roman.gumeniuk@physik.tu-freiberg.de.
Abstract:
Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P4̄3n(α,0,0)000(0,α,0)000(0,0,α)000; a = 8.72328(1) Å, α = 0.4974(2)] modulated crystal structure. A slight shift of the composition towards higher Yb-content (i.e. Yb3.2Co4Ge12.8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pm3̄n, a = 8.74072(2) Å] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature-dependent intermediate valence state varying from +2.60 to +2.66 for the temperature range 85-293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements.
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