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Pascoal G. Pagliuso Grupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS)

Workshop on Digital Design of Materials - 09/2013. Routes for finding superconductors based on structural trends. Pascoal G. Pagliuso Grupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS) Instituto de Física ``Gleb Wataghin'', UNICAMP – Campinas -SP. UC - Irvine. CBPF. Outline.

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Pascoal G. Pagliuso Grupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS)

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  1. Workshop on Digital Design of Materials - 09/2013 Routes for finding superconductors based on structural trends Pascoal G. Pagliuso Grupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS) Instituto de Física ``Gleb Wataghin'', UNICAMP – Campinas -SP UC - Irvine CBPF

  2. Outline I. HFS in similar crystal structures II. The role of dimensionality and crystal structures (CEF – single ion anisotropy) III. Possible relationship with FeAs-based intermetallic IV. The role of local distortion of FeAs bonds V. Substitution effects on the localization character and orbital degrees of freedom of the Fe 3d bands VI. Implications in new materials search and suggestions for digital design

  3. CemMnIn3m+2n CeRh1-x(Ir,Co)xIn5 [1,2] Ce2Rh1-xIrxIn8 [3,4,5] -Ce2CoIn8 TC 1.0 K   600 mJ/K2 mole Ce [3] E.N. Hering et al Physica B, 378, 423 (2006). [4] E.N. Hering, Physica B, 403, 780 (2008); [5] E. N. Hering, C. Adriano, et al, PRB (2011). [1] Pagliuso et al, Physica B, 312, 129 (2002). [2] Pagliuso et al, Phys.Rev B, 64, 100503(R) (2001).

  4. c/a as control parameter for Tc Is there an intrisic parameter in this plot, which depends on c/a and determines TC? Tuning: • JRKKY • TK - CEF P.G. Pagliuso et al. PRB, 100503 (R) (2002);Physica B 312-313, 129 (2002).

  5. RE moments ordered along c-axis. TN evolution for RmAnIn3m+2n(m = 1,2 ; n =0,1) RE moments in the ab-plane. Garcia, E. Miranda, et al. JAP (2006) P.G. Pagliuso et al. Physical Review B. 62, 12266 (2000) also PRB 2001.

  6. INS and XAS CEF study in Ce-M-In T. Willers et al. A. Severing et al. PRB (2010) A.D. Christianson et al PRB (2004).

  7. Extrapolation of CEF trend to Ce-based materials cubic tetragonal TRKKY TK TN anisotropic anisotropic anisotropic isotropic (increasing of g-anisotropy) Strong magnetic-fluctuations?? Frustrated local moments + hybridization

  8. 1-1-5 – FeAs-intermetallics ? Marianne Rotter al. New J. of Phys. (2009). M. S. Torikachvilli et al. PRB 2008.

  9. FeAs-based superconductors • Common Structural parameter: FeAs4 tetrahedral • Common Electronic parameter: SDW magnetic instability J. Paglione and R. L. Greene. Nature Physics 6, 645 (2010).

  10. Resultados – EXAFS E. Granado et al. PRB 83, 184508 (2011)

  11. Site specific ESR on Fe-based Intermetallic Compounds

  12. Ho  g-value or IT H  relaxation and inhomogeneity I   (T)

  13. ESR Results Eu 2+ P. F. S. Rosa et al. PHYSICAL REVIEW B 86, 165131 (2012) P. F. S. Rosa et al. submitted to PRL (2013).

  14. ESR - Results P. F. S. Rosa et al. PHYSICAL REVIEW B 86, 165131 (2012) P. F. S. Rosa et al. submitted to PRL (2013).

  15. z y x

  16. z y x Smaller dFe-As with chemical substitution, hydrostatic pressure and magnetic field in the plane! xy occupation increases SDW Phase vanishes

  17. Implications for designing materials • To increase TC for magnetically mediated SC: Tsf, characteristic T for spin fluctuations high Tunable carrier density • Quasi 2-d helps a lot; maybe not much 2-d needed – increase c/a – tune CEF GS • Need bigger bandwidths to increase Tsf, but keep optimized Tc/Tsf - 3d spins in the active layer. 1-1-5 e 2-1-8 1-2-2 2-1-4, etc

  18. Examples for Digital Design? 2-1-4 2-1-8 1-2-2 1) Bi2CuIn8 3d single band at FS? Which symmetry? 2) CaFeSn5 Fe 3d T2g at the Fermi level? dxy with larger occupation? 3) Yb2CoAs4 Yb3+GS Ising like? Energy scale of 4-electrons?

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