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Superconducting Materials

MAGNETYZM NADPRZEWODNIKÓW NA BAZIE ŻELAZA Eu-122 BADANY METODĄ SPEKTROSKOPII MÖSSBAUEROWSKIEJ 57 Fe i 151 Eu K. Komędera 1 , L. M. Tran 2 , A. Błachowski 1 , K. Ruebenbauer 1 , J. Żukrowski 3,4 , Z. Bukowski 2

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Superconducting Materials

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  1. MAGNETYZM NADPRZEWODNIKÓW NA BAZIE ŻELAZA Eu-122 BADANY METODĄ SPEKTROSKOPII MÖSSBAUEROWSKIEJ 57Fe i 151Eu K. Komędera1, L. M. Tran2, A. Błachowski1, K. Ruebenbauer1, J. Żukrowski3,4, Z. Bukowski2 1Zakład Spektroskopii Mössbauerowskiej, Instytut Fizyki, Uniwersytet Pedagogiczny, Kraków, Polska 2Instytut Niskich Temperatur i Badań Strukturalnych, Polska Akademia Nauk, Wrocław, Polska 3AGH Akademia Górniczo-Hutnicza, Akademickie Centrum Materiałów i Nanotechnologii, Kraków, Polska 4AGHAkademia Górniczo-Hutnicza, Wydział Fizyki i Informatyki Stosowanej, Katedra Fizyki Ciała Stałego, Kraków, Polska ------------------------------------------------------------------------------------------------------ X Ogólnopolskie Seminarium Spektroskopii Mössbauerowskiej OSSM’2014 Wrocław, 15-18 czerwca 2014

  2. Superconducting Materials

  3. Superconductivity in the non-magnetic state of iron under pressureK. Shimizu et al. Nature 412, 316 (2001)hcp Febecomes superconductorat temperatures below 2 Kand at pressures between 15 and 30 GPa

  4. Journal of American Chemical Society Received January 2008, Published online February 2008 --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Up to now the maximum superconducting critical temperature of iron-based superconductors is56 K

  5. Fe-based Superconducting Families pnictogens:P, As, Sb chalcogens:S, Se, Te 111112211111 LnO(F)FeAsAFe2As2AFeAs FeTe(Se,S) Ln = La, Ce, Pr, Nd, Sm, Gd … A = Ca, Sr, Ba, Eu, K A = Li , Na Tscmax = 56 K 47 K 18 K 15 K

  6. Layered Structure of Fe-based Superconductors Spin density wave (SDW) magnetic order --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Phase Diagram Holes, electrons or isovalent doping BaFe2As2 Ba1-xKxFe2As2 BaFe2-xCoxAs2 BaFe2As2-xPx ‘122’ Parent Compounds SDW Doped Compounds  ‘122’ Superconductors

  7. ”122” family of Fe-based superconductors

  8. EuFe2As2 parent compound EuFe2-xCoxAs2 TSDW (Fe) = 190 K TN (Eu) = 19 K

  9. EuFe2As2 Root mean square amplitude of SDW critical exponent 0≈ 0.125universality class (1, 2) ↓ one dimension in the spin space (Ising model) and two dimensions in the real space (magnetic planes)

  10. (Eu1-yCay)(Fe2-xCox)As2 57Fe Mössbauer spectra TN (Eu) = 19 K TSDW = 192 K TSDW  100 K TSDW  80 K lack of SDW filamentary superconductivity Eu2+ Transferred Field on 57Fe

  11. 151Eu Mössbauer spectroscopy

  12. (Eu1-yCay)(Fe2-xCox)As2 151Eu Mössbauer spectra • EuFe2As2 • TSDW (Fe) = 190 K • TN (Eu) = 19 K • Parent • Superconductor Tsc = 9.5 K • Superconductor Tsc = 11 K • Over-doped Eu(2+)   Eu(3+) Eu2+ orders magnetically regardless of the Co-substitution level. Eu2+ moments rotate from a-axis to c-axis. Eu2+magnetism and superconductivity coexist.

  13. Conclusions • The SDW order diminishes in (Eu1-yCay)(Fe2-xCox)As2 with addition of Co and Ca, i.e., a transition temperature is lowered together with the SDW amplitude. • SDW survives across the region of superconductivity and it vanishes in the overdoped region. However, in the region of superconductivity one has some non-magnetic component with the intensity increasing with the Co and Ca substitution. It seems that superconductivity has some filamentary character. • Eu2+ orders magnetically regardless of the Co and Ca substitution . Europium moments rotate from the a-axis in the direction of the c-axis (within a-c plane). Europium magnetic order and superconductivity coexist in the same volume.

  14. Thank you very much for your attention!

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