Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Correlated Electrons: Spin Systems, Itinerant Magnets 2

TT 17.6: Talk

Monday, March 11, 2013, 16:15–16:30, H19

Mössbauer, NMR und µSR investigations of microscopic magnetic ordering of La₂O₂Fe₂OSe₂ — •Sirko Bubel¹, Marco Günther¹, Rajib Sarkar¹, Hans-Henning Klauss¹, Hubertus Luetkens², Gwendolyn Pascua², Kwang-Yong Choi³, and Haidong Zhou⁴ — ¹Institut für Festkörperphysik, Technische Universität Dresden, 01062 Dresden, Germany — ²Paul Scherrer Institut, 5232 Villigen PSI, Switzerland — ³Institut für Physik der Kondensierten Materie, 38106 Braunschweig, Germany — ⁴Experimental Condensed Matter Physics, University of Tennesee

20 years after the first investigations of the antiferromagnetically ordered oxo-chalcogenid La₂O₂Fe₂OSe₂ the common picture of microscopic alignment of iron moments in the expanded squarish Fe₂O-layers is still controversy discussed [1,2]. Furthermore first superconducting samples of this structural class were succesully synthesized in 2012 [3] linking this oxo-chalcogenid to the pnictide superconductors.

To understand the mechanism of iron magnetism in these systems we investigated a powder sample of La₂O₂Fe₂OSe₂ by ⁵⁷Fe-Mössbauer spectroscopy, µSR and ¹³⁹La-NMR. These measurements strongly suggest that iron moments are coupled ferromagnetically via selenium and antiferromagnetically via oxygen. We infer a new magnetic structure on the basis of these results, being consistent with Goodenough-Kanamori-rules, and speculate about orbital order in this system.
[1] Y. Fuwa et al., Phys. Rev. B. 84 (2011) 174506
D. J. Free, S. O. Evans, Phys. Rev. B. 81 (2010) 214433
P. Doan et al., J. Am. Chem. Soc. 134, 16520 (2012)