Nonpareil Yb Behavior in YbMn 6 Ge 6-x Sn x
Abstract
We investigate the temperature dependence of the Yb valence in YbMn 6 Ge 1:8 Sn 4:2 and YbMn 6 Ge 1:6 Sn 4:4 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 ¼ 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.
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