Double superconducting transition in the filled skutterudite PrOs4Sb12 and sample characterizations

TitleDouble superconducting transition in the filled skutterudite PrOs4Sb12 and sample characterizations
Publication TypeJournal Article
Year of Publication2008
AuthorsMeasson MA, Braithwaite D, Lapertot G, Brison JP, Flouquet J, Bordet P, Sugawara H, Canfield PC
Journal TitlePhysical Review B
Date PublishedApr
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberISI:000255457200121
Keywordssusceptibility, TEMPERATURE SPECIFIC-HEAT

Through the characterization of many samples of the filled skutterudite compound PrOs4Sb12, we found that even though the double superconducting transition in the specific heat (T-c1 similar to 1.89 K and T-c2 similar to 1.72 K) appears in samples of good quality, there are various pieces of evidence that cast doubt on its intrinsic nature. First, three samples exhibit a single sharp transition of similar to 15 mK width at T-c similar to 1.7 K. The quality of the samples exhibiting a single transition is clearly better; the width of the transition is smallest and the normalized specific heat jump (C-C-normal)/C-normal)(Tc) is larger than the sum of the two specific heat jumps when a double transition exists. Second, the ratio of the two specific heat jumps Delta C(T-c1)/Delta C(T-c2)exhibits a wide variation with samples not only among different batches but also even within a batch. Finally, this ratio was strongly reduced by polishing a sample down to similar to 100 mu m, which points to bulk inhomogeneities as an origin of the spurious transition. Our x-ray diffraction analysis points to Pr-vacancy problem in the samples, but it does not show that they are the origin of the double transition. We provide the superconducting phase diagram under magnetic field of a sample exhibiting a single transition and fit the curve H-c2(T) with a two-band model taking into account the appropriate values for the gap as deduced from thermal conductivity measurements.

Alternate JournalPhys. Rev. B