Crossover and coexistence of superconductivity and antiferromagnetism in the filled-skutterudite system Pr1-xEuxPt4Ge12

The superconducting and normal-state properties of the filled-skutterudite system Pr1-xEuxPt4Ge12 were studied. Polycrystalline samples were investigated via x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific-heat measurements. Upon Eu substitution, we observed a crossover from superconducting to antiferromagnetic states with a region where both states coexist. In the superconducting region, the specific-heat data exhibit a change of temperature dependence, suggesting an evolution from a nodal to a nodeless superconducting energy gap or a suppression of multiband superconductivity. This change is relatively slower than those reported for different substituent ions, suggesting that paramagnetic impurities have a weaker pair-breaking effect on unconventional superconductivity in PrPt4Ge12. In the normal state, an evolution from Fermi-liquid to non-Fermi-liquid behavior was observed, accompanied by the coexistence of superconductivity and antiferromagnetism, suggesting that the underlying electronic structure is primarily responsible for the complex physical phenomena found in this system.