⁷⁵As-NQR Studies of Filled-Skutterudites PrRu₄As₁₂and LaRu₄As₁₂

Abstract

We report 75 As nuclear quadrupole resonance (NQR) measurements of the filled skutterudite superconductors LaRu4As12 and PrRu4As12. The temperature dependence of 75 As-NQR line and the nuclear spin-lattice relaxation rate 1/T1 show that the Pr 3+ has a crystal electric field (CEF) singlet ground state with a separate first excited state. In the superconducting state of PrRu4As12 and LaRu4As12, 1/T1 has a coherence peak just below the transition temperature and decreases exponentially at low temperatures. This behavior shows that the s-wave superconductivity occurs in both compounds.

Superconducting Properties of Pr-Based Filled Skutterudite PrRu4As12

“…This anomaly is probably due to a magnetic ordering in a secondary phase included in the present sample since no corresponding anomalies appear in recent 75 As-NQR measurements. 22 This phase has not been identified by the x-ray diffraction measurements. To synthesize a sample free from the secondary phase, sample preparation is conducted several times under different conditions and the best sample is used for the present measurements.…”

“…However, a clear coherence peak observed in As-NQR 1/T 1 indicates that such nonuniformity would not be very large. 22 From the C el (T, H) data, the upper critical field µ 0 H c2 (T ) is determined, as shown in the H-vs-T phase diagram of Fig. 2.…”

Electron-phonon superconductivity in the filled skutterudites LaRu4P12, LaRu4As12 , and Tütüncü1, Karaca2, Srivastava3 2017Phys. Rev. B

“…Also, lanthanum compounds display interesting superconducting behavior at low temperatures [37][38][39][40][41][42][43][44][45][46][47]. The superconducting transition temperature (T c ) of LaRu 4 X 12 with X = P, As, Sb is found to be 7.2, 10.3, and 2.8 K [37,38,42,43].…”

Superconducting Properties of LaRu4As12Synthesized at High Pressure

“…In addition, its substituted compound PrRu 4 As 12 is pointed out the possibility of the multiband SC of LaRu 4 As 12 . 13,19 It is also important to realize the origin of the multiband effect observed in PrRu 4 As 12 13 by studying the superconducting properties of the isostructural compound LaRu 4 As 12 . Systematic understanding for such variety in the SC properties of filled skutterudites is one of the important issues.…”