Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 23: Superconductivity: Fe-based Superconductors - Fe(Se/Te)

TT 23.2: Talk

Wednesday, March 28, 2012, 09:45–10:00, H 2053

Phase separation in superconducting and antiferromagnetic Rb_0.8Fe_1.6Se_2.0 probed by Mössbauer spectroscopy — •Vadim Ksenofontov¹, Gerhard Wortmann², Sergey A. Medvedev^1,3, Vladimir Tsurkan^4,5, Joachim Deisenhofer⁴, Alois Loidl⁴, and Claudia Felser¹ — ¹Institut für Anorganische und Analytische Chemie, Johannes Gutenberg-Universität, D-55099 Mainz, Germany — ²Department Physik, Universität Paderborn, D-33095 Paderborn, Germany — ³Max-Planck Institute for Chemistry, D-55128 Mainz, Germany — ⁴Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany — ⁵Institute of Applied Physics, Academy of Sciences, MD-2028, Chisinau, Republic of Moldova

⁵⁷Fe Mössbauer studies of superconducting Rb_0.8Fe_1.6Se_2.0 with T_c = 32.4 K were performed on single-crystalline and polycrystalline samples in the temperature range 4.2 K to 295 K. They reveal the presence of 88% magnetic and 12% non-magnetic Fe²⁺ species with the same polarization dependence of their hyperfine spectra. The magnetic species are attributed to the 16i sites of the √5 × √5 × 1 superstructure and the non-magnetic Fe species to a nano-sized phase observed in recent structural studies of superconducting K_xFe_2−ySe₂ systems. The ⁵⁷Fe spectrum of a single-crystalline sample in an external field of 50 kOe applied parallel to the crystallographic c-axis confirms the antiferromagnetic order between the fourfold ferromagnetic Fe(16i) supermoments and the absence of a magnetic moment at the Fe sites in the minority phase. Our study provides convincing evidence about the nano-scale phase separation in Rb_0.8Fe_1.6Se_2.0.