%0 Journal Article
%T Unconventional magnetism in multivalent charge-ordered YbPtGe$_2$ probed by $^{195}$Pt- and $^{171}$Yb-NMR
%A R. Sarkar
%A R. Gumeniuk
%A A. Leithe-Jasper
%A W. Schnelle
%A Y. Grin
%A C. Geibel
%A M. Baenitz
%J Physics
%D 2013
%I arXiv
%R 10.1103/PhysRevB.88.201101
%X Detailed $^{195}$Pt- and $^{171}$Yb nuclear magnetic resonance (NMR) studies on the heterogeneous mixed valence system YbPtGe$_2$ are reported. The temperature dependence of the $^{195}$Pt-NMR shift $^{195}K(T)$ indicates the opening of an unusual magnetic gap below 200\,K. $^{195}K(T)$ was analyzed by a thermal activation model which yields an isotropic gap $\Delta/k_B \approx 200$\,K. In contrast, the spin-lattice relaxation rate $^{195}$($1/T_1$) does not provide evidence for the gap. Therefore, an intermediate-valence picture is proposed while a Kondo-insulator scenario can be excluded. Moreover, $^{195}$($1/T_1$) follows a simple metallic behavior, similar to the reference compound YPtGe$_2$. A well resolved NMR line with small shift is assigned to divalent $^{171}$Yb. This finding supports the proposed model with two sub-sets of Yb species (di- and trivalent) located on the Yb2 and Yb1 site of the YbPtGe$_2$ lattice.
%U http://arxiv.org/abs/1310.3371v2