Structural changes at the Verwey transition in Fe3O4

Tabiś, Wojciech; Kusz, Joachim; Kim-Ngan, Nhu-Tarnawska Hoa; Tarnawski, Z.; Zontone, Federico; Ka̧kol, Z.; Kozłowski, A.

doi:10.1016/j.radphyschem.2009.02.010

Cited by 5 publications

(2 citation statements)

References 18 publications

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“…The results gathered on sample cooling are presented in Figure 3a and 3b [25]. They suggest that strong lattice reaction goes past some other processes that cause the AC susceptibility to diminish, i.e.…”

Section: How the Transition Proceedsmentioning

confidence: 88%

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Ka̧kol

Kozłowski

Kołodziej

et al. 2015

Philosophical Magazine

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Magnetite is the oldest magnet and the first material where the concept of a strong correlations driven metal-insulator transition was suggested and found at T V = 124 K in the so-called Verwey phase transformation. Recently, the structure below T V was solved revealing subtle electronic structure in the form of trimeron lattice that, according to yet another recent communication, may be switched within femtosecond range. In this review article, we argue that the same change of trimeron lattice can be achieved by a magnetic field, in the phenomenon called the easy axis switching. The results of many of our experiments show that although this process is best viewed by magnetization studies, it is also reflected in magnetostriction, causes some changes in electronic transport and can be observed microscopically by NMR that proved electronic order alteration. All those facts suggest that the axis switching process observed and studied by us is intimately linked with the fast change of electronic trimeron order mentioned above.Probably none of the naturally existing minerals was utilized by mankind and nature more in its pristine form than magnetite. Navigation in the world, both by artificial and natural compasses, storage media and, finally, the tool in the emerging field of spin electronics are a few examples only. But despite its role in civilization, magnetite displays yet another fascinating face: the Verwey transition (VT). In this first-order phase transformation, the resistivity drops two orders of magnitude when heated above T V = 124 K. Surprisingly, all groups of magnetite "application" and the Verwey transition are interwoven: cooling down magnetite below T V results in a drastic drop of electric conductivity, affecting its spintronic application and the thermal cycling across the transition greatly diminishes coercive force, i.e. magnetic memory (see e.g. [1]). This transition is the subject of our extensive studied described below.Not only resistivity jumps at T V ; the spectacular anomalies are observed practically in all physical characteristics. In particular, there is a huge peak in heat capacity, proving first-order character of the transition and the structure symmetry changes. The hightemperature magnetite structure was found of inverse spinel type, with Fd 3m symmetry and with Fe residing in tetrahedral and octahedral positions. When cooled below T V ,

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Section: How the Transition Proceedsmentioning

confidence: 88%

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Ka̧kol

Kozłowski

Kołodziej

et al. 2015

Philosophical Magazine

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“…The possible alternative approach to the unexpected changes in some peaks may concern surface effects and the complicated near-surface structural domains that appear in magnetite structure in the temperature region close to the Verwey transition [52,53]. The near-surface structure is additionally affected by strain developed during sample polishing prior to the experiment [54].…”

Section: A Resonant X-ray Scatteringmentioning

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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XRD, internal field-NMR and Mössbauer spectroscopy study of composition, structure and magnetic properties of iron oxide phases in iron ores

Manjunatha

Kumar

Anupama

et al. 2019

Journal of Materials Research and Technology

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Structural changes at the Verwey transition in Fe3O4

Cited by 5 publications

References 18 publications

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

Charge rearrangement in magnetite: from magnetic field induced easy axis switching to femtoseconds electronic processes

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

XRD, internal field-NMR and Mössbauer spectroscopy study of composition, structure and magnetic properties of iron oxide phases in iron ores

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