Flux Synthesis, Crystal Structures, and Magnetic Ordering of the Rare-Earth Chromium(II) Oxyselenides RE2CrSe2O2 (RE = La-Nd)

Simon Peschke; Valentin Weippert; Anatoliy Senyshyn; Martin Johann Mühlbauer; Oliver Janka; Rainer Pöttgen; Stefan Holenstein; Hubertus Luetkens; Dirk Johrendt

doi:10.1021/acs.inorgchem.6b02895

Flux Synthesis, Crystal Structures, and Magnetic Ordering of the Rare-Earth Chromium(II) Oxyselenides RE₂CrSe₂O₂ (RE = La-Nd)

Inorg Chem. 2017 Feb 20;56(4):2241-2247. doi: 10.1021/acs.inorgchem.6b02895. Epub 2017 Feb 9.

Authors

Affiliations

¹ Department Chemie, Ludwig-Maximilians-Universität München , D-81377 München, Germany.
² Heinz Maier-Leibnitz Zentrum, Technische Universität München , Lichtenbergstrasse 1, D-85747 Garching, Germany.
³ Helmholtz Institute Ulm for Electrochemical Energy Storage , Helmholtzstrasse 11, 89081 Ulm, Germany.
⁴ Institut for Applied Materials, Karlsruhe Institute of Technology , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
⁵ Institut für Anorganische und Analytische Chemie, Universität Münster , Corrensstrasse 30, D-48149 Münster, Germany.
⁶ Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute , CH-5232 Villigen PSI, Switzerland.
⁷ Physik-Institut der Universität Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.

PMID: 28182417
DOI: 10.1021/acs.inorgchem.6b02895

Abstract

The rare-earth chromium(II) oxyselenides RE₂CrSe₂O₂ (RE = La-Nd) were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined by single-crystal and powder X-ray diffraction (Pb₂HgCl₂O₂-type, C2/m, Z = 2). The magnetic structure of La₂CrSe₂O₂ was solved and refined from neutron powder diffraction data. Main building blocks are chains of edge-sharing CrSe₄O₂ octahedra linked together by two edge-sharing ORE₃Cr tetrahedra forming infinite ribbons. The Jahn-Teller instability of divalent Cr²⁺ (d⁴) leads to structural phase transitions at 200 and 130 K in La₂CrSe₂O₂ and Ce₂CrSe₂O₂, respectively. RE₂CrSe₂O₂ are Curie-Weiss paramagnetic above T_N ≈ 14-17 K. Neutron powder diffraction reveals anti-ferromagnetic ordering of the Cr²⁺ moments in La₂CrSe₂O₂ below T_N = 12.7(3) K with an average ordered moment of 3.40(4) μ_B/Cr²⁺ at 4 K, which was confirmed by muon spin rotation experiments.