Site-selective doping of ordered charge states in magnetite

Pachoud, Elise; Cumby, James; Perversi, Giuditta; Wright, Jonathan P.; Attfield, J. Paul

doi:10.1038/s41467-020-15504-5

Cited by 9 publications

(14 citation statements)

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“…[835][836][837] In fact, our understanding of magnetite and of the Verwey transition has significantly improved over the last decade. 835,836,[838][839][840][841] The current understanding is that, at the Verwey temperature, a structural transition from cubic to monoclinic occurs, characterized by a complex lattice distortion that leads to an increase by…”

Section: Electric Field Control Of Charge Ordermentioning

confidence: 99%

“…the high temperature cubic unit cell together with a charge localization process whereby the double-exchange active octahedral Fe cations cluster in a superstructure of trimeron complexes with charge and orbital order. 835,836,841 The iron valence state varies by 0.6 electrons from +2.35 to +2.95 in contrast to a mixed 3+ and 2+ valence state. This variation is for octahedral sites belonging to the trimeron complex.…”

Section: Please Cite This Article Asmentioning

confidence: 99%

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Epitaxial ferroelectric interfacial devices

Vaz

Bibès

Rabe

et al. 2021

Applied Physics Reviews

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Epitaxial ferroelectric interfacial devicesFerroelectric interfacial devices consist of materials systems whose interfacial electronic properties (such as a 2D electron gas or an interfacial magnetic spin configuration) are modulated by a ferroelectric layer set in its immediate vicinity. While the prototypical example of such a system is the ferroelectric field effect transistor first proposed in the 1950s, only with the recent advances in the controlled growth of epitaxial thin films and heterostructures, and the recent physical understanding down to the atomic scale of screening processes at ferroelectric-semiconducting and -metallic interfaces made possible by first principles calculations, have the conditions been met for a full development of the field. In this review, we discuss the recent advances in ferroelectric interfacial systems, with emphasis on the ferroelectric control of the electronic properties of interfacial devices with well ordered (epitaxial) interfaces. In particular, we consider the cases of ferroelectric interfacial systems aimed at controlling the correlated state, including superconductivity, Mott metallic-insulator transition, magnetism, charge, and orbital order, and charge and spin transport across ferroelectric tunnel junctions. The focus is on the basic physical mechanisms underlying the emergence of interfacial effects, the nature of the ferroelectric control of the electronic state, and the role of extreme electric field gradients at the interface in giving rise to new physical phenomena. Such understanding is key to the development of ferroelectric interfacial systems with characteristics suitable for next generation electronic devices based on controlling the correlated state of matter.

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Section: Electric Field Control Of Charge Ordermentioning

confidence: 99%

Section: Please Cite This Article Asmentioning

confidence: 99%

Epitaxial ferroelectric interfacial devices

Vaz

Bibès

Rabe

et al. 2021

Applied Physics Reviews

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“…All of these found the same monoclinic Cc lattice distortion as in pure magnetite. Refinements for a Fe 3(1−δ) O 4 material with estimated hole-doping of 3δ = 0.0116, 53 and for a natural mineral sample of composition Fe 2.986 Al 0.007 Si 0.003 Mg 0.002 Mn 0.002 O 4 54 both gave coordinates similar to those of the SWA model, with the same charge, orbital, and trimeron orders apparent, although with some blurring of the local electronic distortions. However, the refinement of a more heavily doped Fe 3– x Zn x O 4 structure with estimated x = 0.0228 found a remarkable suppression of charge, orbital, and trimeron features at one of the eight Fe 2+ sites within the Cc cell.…”

Section: Resultsmentioning

confidence: 99%

“…This trimeron is selectively destroyed in Fe 2.98 Zn 0.02 O 4 as the arrowed Fe 2+ site is preferentially oxidized. 53 Material reprinted with permission from ref ( 53 ). Copyright 2012, Nature Publishing Group, a division of Macmillan Publishers Limited.…”

Section: Introductionmentioning

confidence: 99%

Magnetism and the Trimeron Bond

Attfield

2022

Chem. Mater.

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A review of progress in understanding the Verwey transition in magnetite (Fe 3 O 4 ) over the past decade is presented. This electronic and structural transition at T V ≈ 125 K was reported in 1939 and has since been a contentious issue in magnetism. Long range Fe 2+ /Fe 3+ charge ordering has been confirmed below the transition from crystal structure refinement, and Fe 2+ orbital ordering and formation of trimerons through weak bonding of Fe 2+ states to two Fe neighbors has been discovered. This model has accounted for many spectroscopic observations such as the 57 Fe NMR frequencies. The trimeron lifetime has been measured, and trimeron soft modes have been observed. The origin of the first to second order crossover of Verwey transitions in doped magnetites has been revealed by a nanoparticle study. Electronic and structural fluctuations are found to persist to temperatures far above T V and local structural distortions track the bulk magnetization, disappearing at the 850 K Curie transition. New binary mixed-valent iron oxides discovered at high pressure are found to have electronic transitions and orbital molecule ground states similar to those of magnetite.

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“…The cubic phase may be regarded as a dynamic collection of less symmetric atomic/electronic arrangements that average to a mean cubic state. The behavior of those arrangements may be linked to the still unresolved problem of the Verwey transition of first and second order [11,12]. With such a variety of phenomena and mutually cooperating subsystems, it is interesting to see to what extent those subsystems can be manipulated by an external trigger, such as an electric field [13], light [14], or a magnetic field [15,16].…”

Section: Introductionmentioning

confidence: 99%

Magnetic field induced structural changes in magnetite observed by resonant x-ray diffraction and Mössbauer spectroscopy

Kołodziej¹,

Bialo

Tabiś

et al. 2020

Phys. Rev. B

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When a magnetic field is applied to a single crystal of magnetite at 124 K > T > 50 K, the monoclinic c M axis, which is the easy magnetization axis, switches to one of the 100 cubic directions, nearest to the direction of the magnetic field, and the phenomenon known as an axis switching (AS) occurs. A global symmetry probe, resonant x-ray scattering, and a local probe, Mössbauer spectroscopy, are used to better understand the mechanism of axis switching. The behavior of three subsystems ordered below the Verwey transition temperature T V , i.e., lattice distortion, an orbital, and charge orderings, was observed via resonant x-ray scattering as a function of an external magnetic field. This was preceded by calculation of selected peak intensities using the FDMNES code. The Mössbauer spectroscopy studies confirmed that the magnetic field triggers electronic rearrangements and atomic displacements. The structure observed after the process of axis switching is very similar to the one obtained after cooling below T V with the magnetic field applied along one of the initial 100 cubic directions and distinct from the cooling in the absence of a magnetic field. From all the experimental observations of the phenomenon done so far, it is clear that AS starts from the fluctuations between octahedral iron orbitals that ultimately lead to the Verwey transition, but also to the higher-temperature trimeron dynamics. Therefore, further observation of the axis switching may be a key point to the understanding of a majority of strongly correlated electronic behavior in magnetite as well as in other transition metal oxides.

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Site-selective doping of ordered charge states in magnetite

Cited by 9 publications

References 25 publications

Epitaxial ferroelectric interfacial devices

Epitaxial ferroelectric interfacial devices

Magnetism and the Trimeron Bond

Magnetic field induced structural changes in magnetite observed by resonant x-ray diffraction and Mössbauer spectroscopy

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