Magnetism and charge ordering in high- and low-temperature phases of Nb2O2F3

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:420

Article

Gapontsev, Vladimir V.¹  Khomskii, Daniel I.²  Streltsov, Sergey V.^1,3 

[1] Russian Acad Sci, Ural Branch, MN Miheev Inst Met Phys, Ekaterinburg 620137, Russia

[2] Univ Cologne, Inst Phys 2, Zulpicher Str 77, D-50937 Cologne, Germany

[3] Ural Fed Univ, Ekaterinburg 620002, Russia

关键词: Dimers;    Charge ordering;   

DOI  :  10.1016/j.jmmm.2016.06.084

来源: Elsevier

【 摘 要 】

It is shown using ab initio band structure calculations that Nb2O2F3 is in the orbital-selective regime in the high -temperature phase (T>90 K), when two electrons occupy singlet molecular orbital, while the magnetic response comes from the remaining single electron in NW23.5+ dimer. The charge order occurs at low temperatures, resulting in the formation of Nb3+-Nb3+- and Nb4+-Nb4+ dimers, which makes this system nonmagnetic. The single electron with unpaired spin is transferred to Nb3+ -Nb3+ dimer, but due to a strong splitting of the bonding xz/yz molecular orbitals the low-spin state with S=0 is stabilized. We argue that the mechanism of the charge ordering in Nb2O2F3 is the gain in kinetic energy related to the formation of molecular orbitals, which occurs due to a strong nonlinear distance dependence of the hopping parameters. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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