Doping Evolution of the Local Electronic and Structural Properties of the Double Perovskite Ba₂Na_1-xCa_xOsO₆

Author(s)

Jagadesh Kopula Kesavan, Dario Fiore Mosca, Samuele Sanna, Francesco Borgatti, Götz Schuck, Phuong Minh Tran, Patrick M. Woodward, Vesna F. Mitrovic, Cesare Franchini, Federico Boscherini

Abstract

We present a combined experimental and computational study of the effect of charge doping in the osmium based double perovskite Ba2Na1–xCaxOsO6 for 0 ≤ x ≤ 1 in order to provide a structural and electronic basis for understanding this complex Dirac–Mott insulator material. Specifically, we investigate the effects of the substitution of monovalent Na with divalent Ca, a form of charge doping or alloying that nominally tunes the system from Os7+ with a 5d1 configuration to Os6+ with 5d2 configuration. After an X-ray diffraction characterization, the local atomic and electronic structure has been experimentally probed by X-ray absorption fine structure at all the cation absorption edges at room temperature; the simulations have been performed using ab initio density functional methods. We find that the substitution of Na by Ca induces a linear volume expansion of the crystal structure which indicates an effective alloying due to the substitution process in the whole doping range. The local structure corresponds to the expected double perovskite one with rock-salt arrangement of Na/Ca in the B site and Os in the B′ one for all the compositions. X-ray absorption near edge structure measurements show a smooth decrease of the oxidation state of Os from 7+ (5d1) to 6+ (5d2) with increasing Ca concentration, while the oxidation states of Ba, Na, and Ca are constant. This indicates that the substitution of Na by Ca gives rise to an effective electron transfer from the B to the B′ site. The comparison between X-ray absorption measurements and ab initio simulations reveals that the expansion of the Os–O bond length induces a reduction of the crystal field splitting of unoccupied Os derived d states.

Organisation(s)

Computational Materials Physics

External organisation(s)

University of Bologna, Institute of Genetics and Biophysics "Adriano Buzzati-Traverso", CNR, Helmholtz-Zentrum Berlin für Materialien und Energie, Ohio State University, Brown University

Journal

Journal of Physical Chemistry C

Volume

124

Pages

16577-16585

No. of pages

9

ISSN

1932-7447

DOI

https://doi.org/10.1021/acs.jpcc.0c04807

Publication date

07-2020

Peer reviewed

Yes

Austrian Fields of Science 2012

104017 Physical chemistry, 103018 Materials physics

Keywords

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials, Energy(all), Surfaces, Coatings and Films, Physical and Theoretical Chemistry

Portal url

https://ucris.univie.ac.at/portal/en/publications/doping-evolution-of-the-local-electronic-and-structural-properties-of-the-double-perovskite-ba2na1xcaxoso6(796af8b0-4f28-4035-b91a-10186a35ce2c).html