Novel Mixed-Valent (V/VI) Triple Perovskite Ruthenates: Observation of a Complex Low Temperature Structural and Magnetic Transition

Author(s)

Katherine E. Stitzer, University of South Carolina - Columbia
Mark D. Smith, University of South Carolina - Columbia
William R. Gemmill, University of South Carolina - Columbia
Hans Conrad zur Loye, University of South Carolina - ColumbiaFollow

Document Type

Article

Subject Area(s)

Chemistry

Abstract

Two new mixed-valent triple perovskites, Ba₃MRu₂O₉ (M = Li, Na), were grown from reactive hydroxide fluxes. They crystallize in the hexagonal space group P6₃/mmc, where Ru(V) and Ru(VI) are disordered on only one crystallographic site. Upon cooling, single crystals of Ba₃NaRu₂O₉ undergo a complex symmetry-breaking structural transition at ca. 225 K from room-temperature hexagonal symmetry to a low-temperature orthorhombic symmetry, space group Cmcm. Accompanying this structural transition is a rather abrupt decrease in the magnetic susceptibility at 210 K followed by a steady decrease in the susceptibility with decreasing temperature. Interestingly, the lithium analogue does not display any structural transition down to 100 K. The structural transition in Ba₃NaRu₂O₉ generates three crystallographically unique Ru sites in the low-temperature structure as compared to only one distinct site in the room-temperature structure. On the basis of an analysis of the Ru−Ru distances in the face-sharing bi-octahedra, the structural transition also appears to involve charge ordering of Ru(V) and Ru(VI), causing all Ru(V) to occupy one set of bi-octahedra and all Ru(VI) to occupy another set.

Publication Info

Published in Journal of the American Chemical Society, Volume 124, Issue 46, 2002, pages 13877-13885.

Rights

Copyright © 2002 American Chemical Society

DOI: 10.1021/ja0271781

Publisher's Version: http://dx.doi.org/10.1021/ja0271781