title: Nonpareil Yb behavior in YbMn6Ge(6-x)Sn(x).
abstract: We investigate the temperature dependence of the Yb valence in YbMn6Ge1.8Sn4.2 and YbMn6Ge1.6Sn4.4 using resonant inelastic x-ray scattering experiments. Yb is found to be in an intermediate valent state in the whole investigated temperature range (10-450 K). We thus prove that the unusually high magnetic ordering temperature of Yb (∼60 and 90 K for x=4.2 and 4.4, respectively) involves an intermediate valent Yb, an unprecedentedly observed phenomenon. Further, an anomalous increase in the Yb valence is observed upon cooling. A scenario is proposed to explain this unusual behavior. It is based on the presence of magnetically ordered Mn moments and on an Anderson Hamiltonian with a Zeeman term modeling the magnetic interactions.
authors.affiliation: Institut Jean Lamour, UMR 7198, Université de Lorraine-Boîte Postale 70239, 54506 Vandœuvre-lès-Nancy, France.
authors.forename: T
authors.initials: T
authors.lastname: Mazet
authors.forename: D
authors.initials: D
authors.lastname: Malterre
authors.forename: M
authors.initials: M
authors.lastname: François
authors.forename: C
authors.initials: C
authors.lastname: Dallera
authors.forename: M
authors.initials: M
authors.lastname: Grioni
authors.forename: G
authors.initials: G
authors.lastname: Monaco