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Pratt, Dan E.; Chang, S.; Taskin, A. A.; Ando, Yoichi; Zarestky, J.; Kreyßig, A.; Goldman, A. I.; McQueeney, R. J.

doi:10.1103/physrevb.87.045127

Cited by 9 publications

(9 citation statements)

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“…Only recently, the elusive charge-ordering pattern in the Verwey phase of magnetite below 120 K was finally solved by means of single crystal X-ray diffraction, and a novel type of quasi-particle consisting of linear units of three iron ions with one shared electron, called a trimeron, was proposed 4 , 5 . This charge ordering is highly unusual and implies a more intricate underlying phenomenon 6 – 8 than ordering of separate Fe 2+ and Fe 3+ ions that takes place, for example, in TbBaFe 2 O 5 9 , 10 or charge ordering during the course of charge disproportionation 11 .…”

Section: Introductionmentioning

confidence: 99%

Pressure tuning of charge ordering in iron oxide

et al. 2018

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A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units of three iron ions with one shared electron, called trimerons. The recently-discovered iron pentoxide (Fe4O5) comprising mixed-valent iron cations at octahedral chains, demonstrates another unusual charge-ordering transition at 150 K involving competing formation of iron trimerons and dimerons. Here, we experimentally show that applied pressure can tune the charge-ordering pattern in Fe4O5 and strongly affect the ordering temperature. We report two charge-ordered phases, the first of which may comprise both dimeron and trimeron units, whereas, the second exhibits an overall dimerization involving both the octahedral and trigonal-prismatic chains of iron in the crystal structure. We link the dramatic change in the charge-ordering pattern in the second phase to redistribution of electrons between the octahedral and prismatic iron chains, and propose that the average oxidation state of the iron cations can pre-determine a charge-ordering pattern.

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Section: Introductionmentioning

confidence: 99%

Pressure tuning of charge ordering in iron oxide

et al. 2018

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“…Upon heating through the Verwey transition, 93% of mixing entropy is supplied to these two ions, and the minority-spin electron relocates mainly into d x y The orbital symmetry thus justifies the intermittent checkerboard order of charges indicated by modulation of the magnetic moment in a combined X-ray and neutrondiffraction study of a TbBaFe 2 O 5 single crystal [29]. This coulombic order is very weak since it prevails when mere 7% of entropy is missing to fully mix the charges.…”

Section: Discussionmentioning

confidence: 99%

Orbital occupancy evolution across spin- and charge-ordering transitions in YBaFe 2 O 5

Lindén

Lindroos

Karen

2017

Journal of Solid State Chemistry

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A B S T R A C TThermal evolution of the Fe 2+ -Fe 3+ valence mixing in YBaFe 2 O 5 is investigated using Mössbauer spectroscopy. In this high-spin double-cell perovskite, the d 6 and d 5 Fe states differ by the single minority-spin electron which then controls all the spin-and charge-ordering transitions. Orbital occupancies can be extracted from the spectra in terms of the (2013)045127. When the remaining 7% of entropy is supplied at a subsequent transition, the mixing electron couples the two Fe atoms predominantly via their d z 2 orbitals. The valence mixing concerns more than 95% of the Fe atoms present in the crystalline solid; the rest is semiquantitatively interpreted as domain walls and antiphase boundaries formed upon cooling through the Néel and Verwey-transition temperatures, respectively.

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“…2(d). Furthermore, for highly stoichiometric TBFO with oxygen excess w < 0.002, an additional phase transition at T * = 310 K precedes the stripe charge ordering transition at T V and is associated with a checkerboard charge ordering [7].…”

Section: Introductionmentioning

confidence: 94%

“…2(b), the magnetic structure used here for the spin dynamics does not include the ferromagnetic c-axis magnetic moment that was obtained from FV neutron diffraction data [6]. The motivation for this difference is that the c-axis magnetization does not have any such increase when warming across T V [7] and moreover the introduction of a c-axis magnetic moment would require an additional irreducible representation to the…”

Section: A Magnetic Structure Unit Cells and Model Interactionsmentioning

confidence: 99%

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Spin waves above and below the Verwey transition in TbBaFe2O5

et al. 2020

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TbBaFe2O5+δ (TBFO) is a mixed valence compound with an antiferromagnetic order (TN=450K) that changes along with the crystal structure and conductivity upon cooling below a Verwey-like transition (TV=280K). This type of double-cell-layered perovskite is useful to study putative charge ordering in fractional valence systems because the crystal structure develops unique sites for the different valence states. While the evolution of the static magnetic structure in the different charge ordered states of TBFO is known, in this study we investigate the effect of charge ordering on the magnetic interactions. Dispersive magnetic excitations measured using single crystal inelastic neutron scattering experiments at T=4KTV are modeled with linear-spin-wave theory to extract anisotropy and superexchange parameters. Below TV, we observe a sizable magnon gap due to an easy-axis magnetic anisotropy that closes above TV due to the evolution of easy-plane anisotropy. The magnetic interactions are found to be highly threedimensional and change across TV. Above TV, where the conductivity is greater, a damping term is required to model the spin waves that suggests a coupling to valence fluctuations.

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Checkerboard to stripe charge ordering transition in TbBaFe2O5

Cited by 9 publications

References 20 publications

Pressure tuning of charge ordering in iron oxide

Pressure tuning of charge ordering in iron oxide

Orbital occupancy evolution across spin- and charge-ordering transitions in YBaFe 2 O 5

Spin waves above and below the Verwey transition in TbBaFe2O5

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