Synthesis, structural and physical properties of δ′-FeSe 1-x

Journal article

We report on synthesis, structural characterization, resistivity, magnetic and thermal expansion measurements on the as yet unexplored δ′-phase of FeSe 1-x, here synthesized under ambient-(AP) and high-pressure (HP) conditions. We show that in contrast to β-FeSe 1-x, monophasic superconducting δ′-FeSe 1-x can be obtained in off-stoichiometric samples with excess Fe atoms preferentially residing in the van der Waals gap between the FeSe layers. The AP δ′-FeSe 1-x sample studied here (T c ≃ 8.5 K) possesses an unprecedented residual resistivity ratio RRR ≃ 16. Thermal expansion data reveal a small feature around ∼90 K, which resembles the anomaly observed at the structural and magnetic transitions for other Fe-based superconductors, suggesting that some kind of "magnetic state" is formed also in FeSe. For HP samples (RRR ≃ 3), the disorder within the FeSe layers is enhanced through the introduction of vacancies, the saturated magnetic moment of Fe is reduced and only spurious superconductivity is observed. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2010.

Authors: De Souza, M; Haghighirad, A; Tutsch, U; Assmus, W; Lang, M

• Journal: European Physical Journal B
• Volume: 77
• Issue: 1
• Pages: 101-107
• Publication date: 2010-09-01
• DOI: 10.1140/epjb/e2010-00254-7
• EISSN: 1434-6036
• ISSN: 1434-6028
• Language: English