Multiple superconducting transitions in the Sr3Ru2O7 region of Sr3Ru2O7-Sr2RuO4 eutectic crystals

We report superconducting properties of Sr3Ru2O7-Sr2RuO4 eutectic crystals, consisting of the spin-triplet superconductor Sr2RuO4 with a monolayer stacking of RuO2 planes and the metamagnetic normal metal Sr3Ru2O7 with a bilayer stacking. Although Sr3Ru2O7 has not been reported to exhibit superconductivity so far, our AC susceptibility measurements revealed multiple superconducting transitions occurring in the Sr3Ru2O7 region of the eutectic crystals. The diamagnetic shielding essentially reached the full fraction at low AC fields parallel to the c axis. However, both the shielding fraction and the onset temperature are easily suppressed by AC fields of larger than 0.1 mT-rms and no anomaly was observed in the specific heat. Moreover, the critical field curves of these transitions have a positive curvature near zero fields, which is different from the upper critical field curve of the bulk Sr2RuO4. These facts suggest that the superconductivity observed in the Sr3Ru2O7 region is not a bulk property. To explain these experimental results, we propose the scenario that stacking RuO2 planes, the building block of superconducting Sr2RuO4, are contained in the Sr3Ru2O7 region as stacking faults.Comment: 8 pages, 10 figures, accepted for publication in Phys. Rev.

Crystal growth of the new Sr2RuO4-Sr3Ru2O7 eutectic system by a floating-zone method

We report the details of Sr2RuO4-Sr3Ru2O7 eutectic crystal growth by the flux-feeding floating-zone technique (FFFZ) under high pressure (lobar). Optimizing the growth conditions. we succeeded in growing eutectic crystals with a regular lamellar structure. The morphology, structure, phase purity. and composition of the crystals were analyzed by means of polarized-light optical microscopy (PLOM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). This new system is expected to be usefull in the study of tunneling and proximity effects between the spin-triplet superconductor Sr2RuO4 and the metamagnetic normal metal Sr3Ru2O7. (c) 2005 Elsevier B.V. All rights reserved.</p

Crystal growth of the new Sr2RuO4-Sr3Ru2O7 eutectic system by a floating-zone method

We report the details of Sr2RuO4-Sr3Ru2O7 eutectic crystal growth by the flux-feeding floating-zone technique (FFFZ) under high pressure (lobar). Optimizing the growth conditions. we succeeded in growing eutectic crystals with a regular lamellar structure. The morphology, structure, phase purity. and composition of the crystals were analyzed by means of polarized-light optical microscopy (PLOM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). This new system is expected to be usefull in the study of tunneling and proximity effects between the spin-triplet superconductor Sr2RuO4 and the metamagnetic normal metal Sr3Ru2O7. (c) 2005 Elsevier B.V. All rights reserved.</p