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Magnetism of the 11 iron-based superconductors parent compound Fe 1+x Te: The Mössbauer study A. Błachowski 1, K. Ruebenbauer 1, P. Zajdel 2, E.E. Rodriguez 3, M.A. Green 3,4 1 Mössbauer Spectroscopy Laboratory, Pedagogical University, Kraków, Poland 2 Division of Physics of Crystals, Institute of Physics, Silesian University, Katowice, Poland 3 NIST Center for Neutron Research, NIST, Gaithersburg, U.S.A. 4 Department of Materials Science and Engineering, University of Maryland, U.S.A. --------------------------------------------------------------------------------------------------------------------------------- IX Ogólnopolskie Seminarium Spektroskopii Mössbauerowskiej OSSM2012, Lublin - Kazimierz Dolny, 10-13 czerwca 2012

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T c max = 56 K 38 K 18 K 15 K Fe-based Superconducting Families pnictogens: P, As, Sb chalcogens: S, Se, Te 1111 122 111 11 LnFeAsO(F) AFe 2 As 2 LiFeAs FeTe(Se,S) Ln = La, Ce, Pr, Nd, Sm, Gd … A = Ca, Sr, Ba, Eu

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Fe 1+x Te x = 0.04 – 0.18 x = 0.06, 0.10, 0.14, 0.18 E.E. Rodriguez et al., Phys. Rev. B 84 064403 (2011)

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Parent Compound Fe 1+y Te Doped Compounds Superconductors y 0 Fe 1+y Te 1-x Se x Fe 1+y Te 1-x S x K. Katayama et al., J. Phys. Soc. Japan 79 113702 (2010) Y. Mizuguchi et al., J. Appl. Phys. 109 013914 (2011)

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Alcoholic beverages induce superconductivity in FeTe 1x S x K. Deguchi et al., Supercond. Sci. Technol. 24 055008 (2011)

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Magnetic-crystallographic phase diagram of the Fe 1+x Te E.E. Rodriguez et al., Phys. Rev. B 84 064403 (2011) S. Rö ler et al., Phys. Rev. B 84 174506 (2011) G.F. Chen et al., Phys. Rev. B 79 140509(R) (2009)

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Fe 1.06 Te

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Fe 1.10 Te

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Fe 1.14 Te

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Fe 1.18 Te

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Fe 1+x Te x=0.06 x=0.10 x=0.14 x=0.18 65 K 4.2 K

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Square root of the mean squared amplitude of SDW versus temperature

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Conclusions Despite existence of the single crystallographic site for the excess iron one sees at least three different kinds of these atoms. Such situation could occur due to the partial filling of the available interstitial sites by iron and due to some ordering of the iron atoms on these sites. The site with the highest magnetic hyperfine field is likely to contain almost isolated ions, i.e., surrounded by the vacancies on the interstitial sites. The magnetism of the excess iron and SDW are coupled one with another. Both kinds of magnetism disappear at the same transition temperature. The critical exponent of the mean squared amplitude of SDW versus temperature indicates that the universality class is close to the (1, 2) class, i.e. the one dimension of the spin space (Ising model) and two spatial dimensions (Fe-Te layers). Interstitial iron has relatively large localized magnetic moment at least for the site with the highest hyperfine field. These moments interact strongly with the electrons having ability to form Cooper pairs and prevent appearance of the superconductivity. One has to remove interstitial iron to have a chance to get superconducting material.

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Clarification as to why alcoholic beverages have the ability to induce superconductivity in Fe 1+d Te 1-x S x K. Deguchi et al., arXiv:1204.0190 (2012) We found that the mechanism of inducement of superconductivity in Fe 1+d Te 1-x S x is the deintercalation of excess Fe from the interlayer sites. Dziękuję za uwagę i na zdrowie!

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