Berlin 2024 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 46: Poster II
MA 46.39: Poster
Donnerstag, 21. März 2024, 15:00–18:00, Poster C
Single-crystal-diffraction studies on the iron-superconductor parent compounds LaFeAsO and SmFeAsO — •Akshay Tewari1, Felix Anger2, Alexandre Bertin1, Bernd Büchner2, Sabine Wurmehl2, and Markus Braden1 — 1II. Phys. Inst., Univ. Cologne, Germany — 2IFW, Dresden, Germany
Iron-based superconductors exhibit a complex interplay between structure, magnetism and superconductivity. Here, we report detailed X-ray diffraction single-crystal structure analyses on the *1111* family of FeAs superconductors REFeAsO, where RE is La or Sm. Previous powder neutron diffraction measurements on LaFeAsO revealed tiny structural anomalies occurring around the structural and magnetic transitions.
The crystal structure is tetragonal at room temperature, and a structural transition occurs at 160-170 K into the orthorhombic phase. In the tetragonal phase we observe reflections violating the h+k=2n condition at low (hk0) values. These peaks are attributed to multiple diffraction arising from the high crystal quality. Below the structural transition, the appearance of orthorhombic domains reduces the crystal quality and thus multiple diffraction. We find no evidence for additional scattering centers (or residual electron density) in the unit cell. Structural anomalies observed for the Fe-As distance and FeAs layer thickness around the transition temperature tend to agree with previous measurements performed using powder data [1]. Anharmonic refinements (up to 4th order) indicate non-harmonic distributions appearing around the La and As atoms near the transition temperatures.
Keywords: Frustration; Neutron Scattering; Xray diffraction; Iron Arsenide