Ce3CuxPt3−xSb4:Modifying the properties of a Kondo insulator by substitutional doping

Abstract

The temperature dependence of the magnetic susceptibility, thermopower, and electrical resistivity were explored for the solid solution ${\mathrm{Ce}}_{3}{\mathrm{Cu}}_{x}{\mathrm{Pt}}_{3\ensuremath{-}x}{\mathrm{Sb}}_{4}.$ The magnetic susceptibility varies from ${\mathrm{Ce}}^{3+}$ Curie-Weiss behavior in ${\mathrm{Ce}}_{3}{\mathrm{Cu}}_{3}{\mathrm{Sb}}_{4}$ to almost ${\mathrm{Ce}}^{4+}$ behavior (intermediate valence) in ${\mathrm{Ce}}_{3}{\mathrm{Pt}}_{3}{\mathrm{Sb}}_{4}.$ All samples had semiconducting resistivities with decreasing activation energies for higher copper concentrations. The large positive thermopower of ${\mathrm{Ce}}_{3}{\mathrm{Pt}}_{3}{\mathrm{Sb}}_{4}$ is greatly affected by small concentrations of copper. The peak of \ensuremath{\sim}300 \ensuremath{\mu}V/K at approximately 110 K for ${\mathrm{Ce}}_{3}{\mathrm{Pt}}_{3}{\mathrm{Sb}}_{4}$ changes to approximately -170 \ensuremath{\mu}V/K for ${\mathrm{Ce}}_{3}{\mathrm{Cu}}_{0.5}{\mathrm{Pt}}_{2.5}{\mathrm{Sb}}_{4}$ at the same temperature. For all the copper-doped samples, the thermopower changes from positive to negative values on cooling.