Investigation of the superconducting and normal state properties of the filled-skutterudite system PrPt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$ via chemical substitution.

We report a systematic chemical substitution study on the unconventional superconductor system PrPt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$, which Sb ions are substituted for Ge. Polycrystalline samples of PrPt$_{\mathrm{4}}$Ge$_{\mathrm{12-}}_{x}$Sb$_{x}$ up to $x=$ 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitutions and evidence for a weak ``rattling'' mode associated with the Pr ions, characterized by a value of $\Theta_{\mathrm{E}} \sim$ 60 K. As part of a systematic study of the effect of various elemental substitutions on the properties of PrPt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$, measurements of the superconducting and normal state properties of the Pr$_{1-x}$Eu$_x$Pt$_4$Ge$_{12}$ system are currently being performed. This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-FG02-04-ER46105 (characterization and physical properties measurements), and the National Science Foundation under Grant No. DMR 1206553 (low-temperature measurements).