Crossing of the crystalline-electric-field and rattling-phonon excitation energies in the filled skutterudite superconductor Pr(Os1-xRu x)4Sb12

Abstract

By specific heat measurements on Pr(Os1-xRux) 4Sb12, we have studied the x-dependences of the 4f-electron crystalline-electric-field first excitation energy and the rattling energy of the Pr ion. The former increases monotonically from ∼ 10 K to ∼ 85 K, while the latter of ∼ 45 K does not change much resulting in a crossing of the two energy levels at x ≃ 0.6. The reported minimum in the superconducting transition temperature Tc at x ≃ 0.6 could be associated with the level crossing. © 2010 IOP Publishing Ltd.