Influence of the crystal field potential on the superconducting properties of PrRu 4Sb 12

Abstract

We have determined the crystal field potential of the superconductor PrRu 4Sb 12 ( T c ∼ 0.9 K ) using inelastic neutron scattering. The ground state of the Pr +3 ions in T h point group symmetry is a Γ 1 singlet with a Γ 5 triplet at an energy of Δ∼5.6 meV. Comparison with recent results on the PrOs 4Sb 12 compound, where T c ∼ 1.85 K and Δ∼0.6 meV, supports the conjecture that inelastic quadrupolar fluctuations (or aspherical Coulomb scattering) are responsible for the strong enhancement of T c . In PrRu 4Sb 12, the effect is reduced by the higher energy of the first excited level.