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Impurity Phases, Stoichiometry, Second Anomaly, and Broad Superconducting Transition in Noncentrosymmetric CePt 3 Si

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. Collaborators. Dr. W. Brämer-Escamilla. IVIC, Caracas.

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Impurity Phases, Stoichiometry, Second Anomaly, and Broad Superconducting Transition in Noncentrosymmetric CePt 3 Si

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  1. Impurity Phases, Stoichiometry, Second Anomaly, and Broad Superconducting Transition in Noncentrosymmetric CePt3Si Ismardo Bonalde Low Temperature Laboratory Center for Physics Venezuelan Institute for Scientific Research

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

  3. Content CePt3Si : Experiments Puzzling previous results : • Broad transition, anomaly 0.5 K, low TC • - Possible origins Present results: • WDX/EDX spectra • - Magnetic penetration depth Conclusions Center for Physics, Low Temperature Laboratory I. Bonalde

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

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

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

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

  8. Puzzling previous results Anomaly 0.5 K and low TC SC (Bridgman) SC (Bridgman) SC (Bridgman, annealed) SC (Bridgman) Yogi et al., J. Phys. Soc. Japan 75, 013709 (06) Izawa et al., Phys. Rev. Lett. 94, 197002 (05) 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

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

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

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

  12. Present results Now we present penetration depth data in single crystals Focus on: stoichiometry second phases transition broadness anomaly at 0.5 K Center for Physics, Low Temperature Laboratory I. Bonalde

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

  14. Present results WDX/EDX and magnetic penetration depth crystals A-1 unannealed TC=0.75 K Ce1.14Pt3Si0.58 host phase impurity phase Center for Physics, Low Temperature Laboratory I. Bonalde

  15. Present results WDX/EDX and magnetic penetration depth crystals A-2 unannealed TC=0.73 K Ce1.61Pt3Si0.91 single phase Center for Physics, Low Temperature Laboratory I. Bonalde

  16. Present results WDX/EDX and magnetic penetration depth crystals B-1 Bridgman(“annealed”) TC=0.79 K Ce0.99Pt3Si1.14 impurity phase host phase 0.55 K Center for Physics, Low Temperature Laboratory I. Bonalde

  17. Present results WDX/EDX and magnetic penetration depth crystals B-2 Bridgman(“annealed”) TC=0.79 K Ce1.04Pt3Si1.07 single phase 0.53 K Center for Physics, Low Temperature Laboratory I. Bonalde

  18. Present results magnetic penetration depth Single phase Ce1.04Pt3Si1.07 Bridgman method high TC (onset) In single crystals impurity phases: X stoichiometry: X ~ 0.53 K annealing: Center for Physics, Low Temperature Laboratory I. Bonalde

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

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

  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 CePt3Si. 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. Center for Physics, Low Temperature Laboratory I. Bonalde

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