Journal article

Publication year: 2020

Pages: 024419-

Journal: Physical Review B

Volume number: 101

Issue number: 2

ISSN: 2469-9950

Open access status: Green

DOI Link: https://doi.org/10.1103/PhysRevB.101.024419

Publisher: American Physical Society

Abstract: 

Recently, a Verwey-type transition in the mixed-valence alkali sesquioxide Cs₄O₆ was deduced from the charge ordering of molecular peroxide O-2(2-) and superoxide O-2(-) anions accompanied by the structural transformation and a dramatic change in electronic conductivity [Adler et al., Sci. Adv. 4, eaap7581 (2018)]. Here, we report that in the sister compound Rb₄O₆, a similar Verwey-type charge ordering transition is strongly linked to O-2(-) orbital and spin dynamics. On cooling, a powder neutron diffraction experiment reveals a charge ordering and a cubic-to-tetragonal transition at T-CO = 290 K, which is followed by a further structural instability at T-s = 92 K that involves an additional reorientation of magnetic O-2(-) anions. Magnetic resonance techniques supported by density functional theory computations suggest the emergence of a peculiar type of pi*-orbital ordering of the magnetically active O-2(-) 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 pi* 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.

Harvard Citation style: Knaflic, T., Jeglic, P., Komelj, M., Zorko, A., Biswas, P., Ponomaryov, A., et al. (2020) Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4O6, Physical Review B, 101(2), p. 024419. https://doi.org/10.1103/PhysRevB.101.024419

APA Citation style: Knaflic, T., Jeglic, P., Komelj, M., Zorko, A., Biswas, P., Ponomaryov, A., Zvyagin, S., Reehuis, M., Hoser, A., Geiß, M., Janek, J., Adler, P., Felser, C., Jansen, M., & Arcon, D. (2020). Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4O6. Physical Review B. 101(2), 024419. https://doi.org/10.1103/PhysRevB.101.024419