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Magnetyzm i nadprzewodnictwo w związkach na bazie EuFe 2 As 2

Magnetyzm i nadprzewodnictwo w związkach na bazie EuFe 2 As 2 - badania metodą spektroskopii Mössbauera A. Błachowski 1 , K. Komędera 1 , J. Gatlik 1 , J. Żukrowski 2 , Z. Bukowski 3 1 Laboratorium Spektroskopii Mössbauerowskiej, Instytut Fizyki, Uniwersytet Pedagogiczny, Kraków

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Magnetyzm i nadprzewodnictwo w związkach na bazie EuFe 2 As 2

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  1. Magnetyzm i nadprzewodnictwo w związkach na bazie EuFe2As2 - badania metodą spektroskopii Mössbauera A. Błachowski1, K. Komędera1, J. Gatlik1, J. Żukrowski2, Z. Bukowski3 1 Laboratorium Spektroskopii Mössbauerowskiej, Instytut Fizyki, Uniwersytet Pedagogiczny, Kraków 2 Akademickie Centrum Materiałów i Nanotechnologii, Akademia Górniczo-Hutnicza, Kraków 3 Instytut Niskich Temperatur i Badań Strukturalnych, Polska Akademia Nauk, Wrocław ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  2. Plan referatu 1.Nadprzewodniki na bazie żelaza 2. EuFe2As2 3. Spektroskopia Mössbauera 57Fe i 151Eu 4.Wyniki EuFe2-xCoxAs2 Eu1-xCaxFe2As2 Eu1-xCax(Fe1-yCoy)2As2 EuFe2-xNixAs2 5.Podsumowanie ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  3. Superconductivity in the non-magnetic state of iron under pressureK. Shimizu et al. Nature 412, 316 (2001)hcp -Fe becomes superconductor at temperature below 2 K and pressure 20 GPa Schematic pressure-temperature phase diagram of iron

  4. •H3S 203 K , 150 GPa 30 GPa) •FeSe s-l •LaH10 260 K , 190 GPa Up to now the maximum Tc is 56 K Published on Web 02/23/2008

  5. Fe-based Superconducting Families pnictogens:P, As chalcogens:S, Se, Te BaFe2As2 SrFe2As2 CaFe2As2 EuFe2As2 KFe2As2 RbFe2As2 CsFe2As2 nonsuperconductingparentcompounds low Tcsuperconductors

  6. Magnetic structure of EuFe2As2 • Twomagneticsublattices • Fe2+ 3d itinerantelectrons • Spin DensityWave • Fe saturation moment 0.99µBalong aaxis • TSDW = 190 K • Eu2+ 4f localisedelectrons • A-typeAntiferromagnet , µeff= 7.94 µBTN = 19 K Y. Xiao et al. PRB 80, 174424 (2009)

  7. EuFe2As2 - pressure-effects K. Matsubayashiet al. PRB 84, 024502 (2011) N. Kurita et al. PRB 83, 214513 (2011) Z. Yu et al. Sci. Rep. 4, 7172 (2014) R.S. Kumar et al.Appl. Phys. Lett. 104, 042601(2014)

  8. ______________Parent compound______________ EuFe2As2 TSDW = 190 K , TN = 19 K _________Superconductors_________ Eu1-xKxFe2As2 Eu(Fe1-xCox)2As2 EuFe2(As1-xPx)2 hole-dopingelectron-dopingisovalent-substitution x = 0.50x = 0.14x = 0.30 Tsc = 32 K Tsc = 11 K Tsc = 27 K J. Maiwald et al. PRB 85, 024511 (2012) W.T. Jinet al. PRB 94, 184513 (2016) G. Caoet al. J. Phys: Cond. Matt. 23, 464204 (2011)

  9. Mössbauer Spectroscopy recoilless nuclear resonance absorption of -rays -ray energy is modulated by the Doppler effect due to the source motion vs. absorber (studied sample) Source (e.g. 57Co/Rh) Absorber (57Fe) Detector 1 mm/s 48neV – v +v

  10. Hyperfine Interactions between Nuclei and Electrons  Mössbauer Parameters Electric Monopole InteractionIsomer Shift S Electron density  S S Electric Quadrupole InteractionQuadrupole Splitting Electric Field Gradient EFG S  1 mm/s3.4el./Bohr3 EFG EQ EFG 1 mm/s5.7 1021V/m2 S Magnetic Dipole InteractionMagnetic Splitting Magnetichyperfine fieldB B B -Fe33 Tesla Fe2O3 52 Tesla BaFe2As2 5.3 Tesla

  11. Electric Field Gradient + Magnetic Hyperfine Field IS EFG B = 10 T  = 0°  = 90° EFG +B EFG +B

  12. Spin density wave (SDW) perpendicular longitudinal commensurate or incommensurate h2n-1 – amplitudes of subsequent harmonics q – wave number of SDW x – relative position of the resonant nucleus along propagation direction of the stationary SDW

  13. Spin density wave (SDW)seen by Mössbauer Spectroscopy h2n-1 – amplitudes of subsequent harmonics q – wave number of SDW x – relative position of the resonant nucleus along propagation direction of SDW SDWhyperfine field distribution57Fe Mössbauer spectrum

  14. 151EuMössbauer spectroscopy Nuclear energy levels for 151Eu in the presence of a magnetic hyperfine interaction

  15. 151EuMössbauer spectroscopy Electric Field Gradient + Magnetic hyperfine field

  16. EuFe2As2 57Fe Mössbauer spectra 151Eu Mössbauer spectra Shape of SDW B = 27.4 T  = 90º TSDW = 192 K 0 = 0.124 Mean squared amplitude of SDW vs. temperature

  17. EuFe2-xCoxAs2 W.T. Jinet al. PRB 94, 184513 (2016)

  18. EuFe2-xCoxAs2 57Fe Mössbauer spectra TN (Eu) = 19 K TSDW = 190 K TSDW = 100 K lack of SDW Eu2+ Transferred Field on 57Fe

  19. EuFe2-xCoxAs2 151Eu Mössbauer spectra Eu(2+)  Parent • Superconductor Tsc = 9.5 K Over-doped  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.

  20. Eu1-xCaxFe2As2 Relative Resistivity

  21. Eu1-xCaxFe2As2 57Fe Mössbauer spectra

  22. Eu1-xCaxFe2As2 Mean squared amplitude of SDW and spectral shift vs. temperature Shape of SDW and distribution of hyperfine magnetic field qD - Debye temperature

  23. Eu1-xCax(Fe1-yCoy)2As2 re-entrant superconductor : Tsc = 12 K and Tre = 10 K 57Fe Mössbauer spectra Relative Resistivity TF about 1 Tesla transferred magneticfield from Euto Fe

  24. 151Eu Mössbauer spectra

  25. EuFe2-xNixAs2 no evidenceofsuperconductivitydown to 1.8 K Z. Ren et al. PRB 79, 094426(2009)

  26. EuFe2-xNixAs2 57FeMössbauer spectroscopy Bt - transferred magneticfield from Euto Fe

  27. EuFe2-xNixAs2 151Eu Mössbauer spectroscopy 165.6(1)°  Eu2+ moments rotate from a-axis to c-axis Magnetic spiral in EuNi2As2 W.T. Jin, …, Z. Bukowski et al. PRB 99, 014425 (2019)

  28. Podsumowanie: Dla EuFe2As2 1.Podstawienie Fe atomami Co lub Ni powoduje:  stopniowy zanik porządku magnetycznego SDW • reorientację momentów magnetycznych Eu z osi a w kierunku osi c  pojawienie się nadsubtelnego pole transferu od Eu na Fe o wartości około 1 T  dla Co pojawienie się nadprzewodnictwa i brak nadprzewodnictwa dla Ni 2. Podstawienie Eu atomami Ca powoduje: • wzrost temperatury porządkowania SDW • brak reorientacji momentów Eu  brak pola transferu od Eu na Fe 3.Obydwie podsieci magnetyczne są silnie sprzężone ze sobą. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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