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LnFeAsO single crystals grown at high pressure: influence of doping and substitutions on superconducting properties and structure

Janusz Karpinski 1Nikolai D. Zhigadlo 2Sergiy Katrych 1Philip J. Moll 2K. Rogacki 3Roman Puzniak 4Andrea Pisoni 1Bertram Batlogg 2Stephen Weyeneth 5Hugo Keller 5Laszlo Forro 1

1. Institute of Condensed Matter Physics EPFL, Ecublens, Lausanne 1015, Switzerland
2. Laboratory for Solid State Physics ETH (ETH), Schafmatstr. 16, Zürich 8093, Switzerland
3. Polish Academy of Sciences, Institute of Low Temperature and Structure Research (INTiBS), Okólna 2, Wrocław 50-422, Poland
4. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
5. Physik-Institut der Universität Zürich, Winterthurerstrasse 190, Zürich CH-8057, Switzerland


For the investigations of intrinsic properties relevant for applications of FeAs based superconductors studies on single crystals are necessary. LnFeAsO  (Ln=La, Pr, Nd, Sm, Gd) single crystals were grown from flux at high-pressure of 30 kbar. Two kind of fluxes have been used: NaCl/KCl and NaAs/KAs. An overview of the basic superconducting properties measured on single crystals of LnFeAsO will be presented.  LnFeAsO compounds show the highest Tc up to 55K and the highest upper critical fields. Superconductivity in LnFeAsO single crystals has been induced by partial substitution of O by F or by H, Sm by Th, Fe by Co, As by P or by oxygen deficiency. Single crystal structure investigations show structure modifications due to substitutions which are linked to superconducting properties. Especially substitution of H for O is important, because it allows much higher doping rate than substitution of F for O. Detailed study of the transport properties of SmFeAs(O,F) single crystals reveals a promising combination of high (> 2 106 A/cm2) and nearly isotropic critical current densities up to 30 T at low temperatures. In the frame of these studies new superconductor related to LnFeAsO, but with much larger c lattice parameter with Tc up to 40K has been discovered. Properties of new superconductor will be presented.

  1. J. Karpinski, Phil. Mag. 92 (2012) 2662.
  2. Philip J.W. Moll et al., Nature Mat. 12 (2012) 134.

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Presentation: Invited oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 1, by Janusz Karpinski
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-11 10:43
Revised:   2013-04-11 10:55