Pseudogap Behavior in Fully Filled Skutterudite YbFe4Sb12 Detected by Sb NQR

This is the authors' abstract. We don't add key points for this paper.

We report the results of 121,123Sb-nuclear quadrupole resonance (NQR) measurements on the fully filled skutterudite YbFe4Sb12 synthesized under high pressure, and compare them with those for an Yb-deficient sample synthesized under ambient pressure in order to elucidate the intrinsic behavior and the effects of the Yb-site filling fraction on magnetic properties. The NQR spectra for the fully filled sample remain narrow down to 1.5 K, indicating no sign of a phase transition, in contrast to the results of the Yb-deficient sample. The nuclear spin–lattice relaxation rate divided by temperature, 1/T1T, is composed of two terms as 1/T1T = (1/T1T)χ + (1/T1T)PG. The first term (1/T1T)χ is scaled to the magnetic susceptibility, which is similar to the behavior of nearly ferromagnetic metals. The pseudogap behavior, related to the second term (1/T1T)PG, is consistent with the optical conductivity measurements, and is a characteristic of the filled skutterudites with a divalent filler ion.