Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4 O6

Knaflic T, Jeglic P, Komelj M, Zorko A, Biswas PK, Ponomaryov AN, Zvyagin SA, Reehuis M, Hoser A, Geiss M, Janek J, Adler P, Felser C, Jansen M, Arcon D (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Physical Review B American Physical Society

Book Volume: 101

Article Number: 024419

Journal Issue: 2

DOI: 10.1103/PhysRevB.101.024419

Abstract

Recently, a Verwey-type transition in the mixed-valence alkali sesquioxide Cs4O6 was deduced from the charge ordering of molecular peroxide O22- and superoxide O2- anions accompanied by the structural transformation and a dramatic change in electronic conductivity [Adler, Sci. Adv. 4, eaap7581 (2018)2375-254810.1126/sciadv.aap7581]. Here, we report that in the sister compound Rb4O6, a similar Verwey-type charge ordering transition is strongly linked to O2- orbital and spin dynamics. On cooling, a powder neutron diffraction experiment reveals a charge ordering and a cubic-to-tetragonal transition at TCO=290 K, which is followed by a further structural instability at Ts=92 K that involves an additional reorientation of magnetic O2- anions. Magnetic resonance techniques supported by density functional theory computations suggest the emergence of a peculiar type of π∗-orbital ordering of the magnetically active O2- units, which promotes the formation of a quantum spin state composed of weakly coupled spin dimers. These results reveal that as in 3d transition-metal compounds, also in the π∗ open-shell alkali sesquioxides the interplay between Jahn-Teller-like electron-lattice coupling and Kugel-Khomskii-type superexchange determines the nature of orbital ordering and the magnetic ground state.

Involved external institutions

Jožef Stefan Institute SI Slovenia (SI) Rutherford Appleton Laboratory GB United Kingdom (GB) Helmholtz-Zentrum Dresden-Rossendorf (HZDR) DE Germany (DE) Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) DE Germany (DE) Justus-Liebig-Universität Gießen DE Germany (DE) Max-Planck-Institut für Chemische Physik fester Stoffe (MPI CPfS) / Max Planck Institute for Chemical Physics of Solids DE Germany (DE)

How to cite

APA:

Knaflic, T., Jeglic, P., Komelj, M., Zorko, A., Biswas, P.K., Ponomaryov, A.N.,... Arcon, D. (2020). Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4 O6. Physical Review B, 101(2). https://doi.org/10.1103/PhysRevB.101.024419

MLA:

Knaflic, T., et al. "Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4 O6." Physical Review B 101.2 (2020).

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