Detailed study of the ac susceptibility of Sr2RuO4 in oriented magnetic fields -: art. no. 214514

We have investigated the ac susceptibility of the spin-triplet superconductor Sr2RuO4 as a function of magnetic field in various directions at temperatures down to 60 mK. We have focused on the in-plane field configuration (polar angle thetasimilar or equal to90degrees), which is a prerequisite for inducing multiple superconducting phases in Sr2RuO4. We have found that the previous attribution of a pronounced feature in the ac susceptibility to the second superconducting transition itself is not in accord with recent measurements of the thermal conductivity or of the specific heat. We propose that the pronounced feature is a consequence of additional involvement of vortex pinning originating from the second superconducting transition.