1. Impurity Phases, Stoichiometry, Second Anomaly, and Broad Superconducting Transition in Noncentrosymmetric CePt 3 Si Ismardo Bonalde Low Temperature Laboratory Center for Physics Venezuelan Institute for Scientific Research

2. Collaborators Dr. W. Brämer-Escamilla R. Ribeiro IVIC, Caracas Prof. C. Rojas UCV, Caracas Prof. E. Bauer Prof. Y. Haga TUW, Vienna JAEA, Ibaraki Center for Physics, Low Temperature Laboratory I. Bonalde

3. Content ExperimentsCePt 3 Si : - Broad transition, anomaly 0.5 K, low T C - Possible origins Conclusions Present results: - WDX/EDX spectra - Magnetic penetration depth Puzzling previous results : Center for Physics, Low Temperature Laboratory I. Bonalde

4. PUZZLING PREVIOUS RESULTS Center for Physics, Low Temperature Laboratory I. Bonalde

5. Puzzling previous results Young et al., Phys. Rev. Lett. 94, 107001 (05) Broad transition and anomaly 0.5 K Center for Physics, Low Temperature Laboratory I. Bonalde polycrystalline (annealed) Bonalde et al., Phys. Rev. Lett. 94, 207002 (05) 0.52 K Bauer et al., Phys. Rev. Lett. 92, 027003 (04) 0.68 K 0.75 K

6. Puzzling previous results Scheidt et al., J. Phys.: Condens. Matter 17, L121 (05) Kim et al., Phys. Rev. B 71, 212505 (05) Broad transition and anomaly 0.5 K Center for Physics, Low Temperature Laboratory I. Bonalde second superconducting transition Ce deficiency Si excess magnetically ordered second phase polycrystalline (quenched) polycrystalline (unannealed)

7. Puzzling previous results Nakatsuji et al., J. Phys. Soc. Japan 75, 084717 (06) Broad transition and anomaly 0.5 K Center for Physics, Low Temperature Laboratory I. Bonalde second superconducting transition single crystals (Bridgman) quenched

8. Izawa et al., Phys. Rev. Lett. 94, 197002 (05) Anomaly 0.5 K and low T C Puzzling previous results Yogi et al., J. Phys. Soc. Japan 75, 013709 (06) Takeuchi et al., J. Phys. Soc. Japan 76, 014702 (07) Tateiwa et al., J. Phys. Soc. Japan 74, 1903 (05) Center for Physics, Low Temperature Laboratory I. Bonalde SC (Bridgman) SC (Bridgman, annealed) SC (Bridgman)

9. Center for Physics, Low Temperature Laboratory I. Bonalde Puzzling previous results Motoyama et al., J. Phys. Soc. Japan 77, 044710 (08) Motoyama et al., J. Phys. Soc. Japan 75, 013706 (06) Anomaly 0.5 K and low T C polycrystalline polycrystalline (annealed) stoichiometry matters

10. Center for Physics, Low Temperature Laboratory I. Bonalde Puzzling previous results broad transition, anomaly 0.5 K, and low T C second peak unannealed/quenched polycrystals low T C (~ 0.5 K) single crystals (Bridgman) annealed polycrystals specific heat thermal conductivity NMR properties penetration depth susceptibility broad transitions T C (onset) ~ 0.75 K off-stoichiometry unannealed and annealed polycrystals second phases unannealed polycrystals

11. PRESENT RESULTS Center for Physics, Low Temperature Laboratory I. Bonalde

12. Present results Focus on: stoichiometry second phases transition broadness anomaly at 0.5 K Now we present penetration depth data in single crystals

13. Center for Physics, Low Temperature Laboratory I. Bonalde Techniques Present results WDX (Wavelenght Dispersive X-ray) analysis (more accurate than EDX) JEOL Electron Probe Microanalyzer (EPMA), model Superprobe 8900R Images: Stoichiometry: EDX - backscattered electrons Magnetic penetration depth tunnel diode oscillator at 13 MHz low ac probing field < 1 mOe temperatures down 40 mK

14. Center for Physics, Low Temperature Laboratory I. Bonalde Present results crystals A-1 unannealedT C =0.75 K host phase Ce 1.14 Pt 3 Si 0.58 impurity phase WDX/EDX and magnetic penetration depth

15. Center for Physics, Low Temperature Laboratory I. Bonalde Present results crystals A-2 unannealed T C =0.73 K single phase Ce 1.61 Pt 3 Si 0.91 WDX/EDX and magnetic penetration depth

16. Center for Physics, Low Temperature Laboratory I. Bonalde Present results crystals B-1 Bridgman (“annealed”) T C =0.79 K host phase Ce 0.99 Pt 3 Si 1.14 impurity phase WDX/EDX and magnetic penetration depth 0.55 K

17. Center for Physics, Low Temperature Laboratory I. Bonalde Present results crystals B-2 Bridgman (“annealed”) T C =0.79 K single phase Ce 1.04 Pt 3 Si 1.07 WDX/EDX and magnetic penetration depth 0.53 K

18. Center for Physics, Low Temperature Laboratory I. Bonalde Present results magnetic penetration depth Single phase Ce 1.04 Pt 3 Si 1.07 Bridgman method high T C (onset) impurity phases: X annealing: stoichiometry: X ~ 0.53 K In single crystals

19. Center for Physics, Low Temperature Laboratory I. Bonalde Present results magnetic penetration depth

20. Center for Physics, Low Temperature Laboratory I. Bonalde Bonalde et al., Physica C 460, 659 (07) Other results superfluid density

21. CONCLUSIONS Center for Physics, Low Temperature Laboratory I. Bonalde

22. Conclusions As opposed to specific heat, in penetration depth measurements the onset is always around 0.75 K The annealing of the samples seems to be a quite important variable in the search for the intrinsic superconducting properties of CePt 3 Si. Second phases and slightly off-stoichiometry appear to play no major roles Something intrinsic seems to be occuring around 0.5 K The linear behavior at low temperatures does not depend on samples.