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Regensburg 2010 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 52: Electronic Properties II

MM 52.2: Vortrag

Donnerstag, 25. März 2010, 11:45–12:00, H5

FeSe1−x synthesized under ambient- and high-pressure conditions: a comparative study — •Mariano de Souza, Amir-Abbas Haghighirad, Ulrich Tutsch, Sebastian Köhler, Daniel Hofmann, Michael Lang, and Wolf Assmus — Physikalisches Institut, Goethe-Universität, Max-von-Laue Str. 1, D-60438 Frankfurt (M), Germany

Among the Fe-based superconducting (SC) materials, the binary alloy FeSe1−x with Tc ≃ 8.5 K [1] has attracted enormous interest. Although a tetragonal-to-orthorhombic transition at high-T takes place, it is not accompanied by long-range magnetic ordering, as it occurs in other Fe-based superconductors. Many questions remain still open, like the right stoichiometry of the SC phase, the symmetry of the SC order parameter and the origin of the high-pressure dependence of Tc [2]. Here, we report resistivity, susceptibility and thermal expansion data on single-crystalline FeSe0.95 prepared under ambient- and high-pressure (HP) conditions. We show that SC samples of FeSe1−x can also be obtained well outside the composition range reported in the literature [3]. Our thermal expansion results reveal a tiny feature around ∼90 K, most likely related to the structural phase transition, and onset of superconductivity around 8.5 K. For samples synthesized under HP conditions, the saturated magnetic moment of Fe is dramatically reduced and superconductivity is destroyed. [1] F.-C. Hsu et al., Proc. Natl. Acad. Sci. U.S.A. 105, 1462 (08); [2] S. Medvedev et al., Nat. Mat. 8, 576 (09); [3] T.M. McQueen et al., Phys. Rev. B 79, 014522 (08).

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