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TT: Fachverband Tiefe Temperaturen
TT 36: Superconductivity: Fe-based Superconductors - Fe(Se,Te), LiFeAs, and other Materials
TT 36.7: Vortrag
Mittwoch, 13. März 2013, 11:15–11:30, H18
Structural phase transitions in the vicinity of putative tricritical point in Fe1+yTe — Cevriye Koz, •Sahana Rössler, Alexander A. Tsirlin, Steffen Wirth, and Ulrich Schwarz — Max Planck Institute for Chemical Physics of Solids, Nöthnizer Straße 40, 01187, Dresden, Germany
Fe1+yTe, the parent compound to the chalcogenide superconductors displays a complex phase diagram with several structural and magnetic phase transitions within the homogeneity range 0.06 ≤ y ≤ 0.15. The control parameters such as external pressure and excess Fe content (y) have similar influence on the phase transitions [1, 2]. Upon increasing y, the first-order transition temperature systematically decreases from 70 K to 58 K. For y ≥ 0.12, two transitions occur: first a continuous magnetic transition followed by a first-order structural transition at a lower temperature. This behavior suggests the presence of a tricritical point close to this composition. We present low-temperature synchrotron powder x-ray diffraction studies on Fe1+yTe in the vicinity of this putative tricritical point. From a careful analysis of the powder diffraction patterns and the temperature dependence of the peak-width, we conclude that for y ≥ 0.12 the phase transitions are sluggish due to a strong competition between different phases. We present a revised temperature-composition phase diagram for Fe1+yTe based on the temperature dependence of the crystal structure, specific heat, and magnetization measurements.
[1] Rößler et al. Phys. Rev. B, 84, 174506 (2011)
Koz et al. Phys. Rev. B, 86, 094505 (2012)