Optical properties of magnetite (Fe<sub>3</sub>O<sub>4</sub>)

Schlegel, A.; Alvarado, S. F.; Wächter, P.

doi:10.1088/0022-3719/12/6/027

Cited by 208 publications

(133 citation statements)

References 28 publications

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“…This study is noteworthy because IRAS was used to show that the formate is bound in a bidentate configuration; it is the first example of IRAS being performed on a Fe 3 O 4 single crystal, and one of a limited number of IRAS studies performed on metal oxide single crystals to date. Interestingly, the absorption peaks exhibit a Fano-like line shape ( Figure 74) because the real and complex parts of the dielectric function of Fe 3 O 4 are comparable in the IR regime (Re(ε) = 13, Im(ε) = 10) [52], and the sample is both a conductor and a dielectric. Similar peak shapes were observed on metallic samples with poor conductivity, but the phenomenon was not previously observed on a metal oxide.…”

Section: Formic Acid (Hcooh)mentioning

confidence: 99%

Iron oxide surfaces

Parkinson

2016

Surface Science Reports

487

463

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The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), hematite (α-Fe 2 O 3 ), and wüstite (Fe 1-x O) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe 3 O 4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment, and because it is an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed.The best understood iron oxide surface at present is probably Fe 3 O 4 (100); the structure is known with a high degree of precision and the major defects and properties are well characterised. A major factor in this is that a termination at the Fe oct -O plane can be reproducibly prepared by a variety of methods, as long as the surface is annealed in 10 Such straightforward preparation of a monophase termination is generally not the case for other iron oxide surfaces. All available evidence suggests the oft-studied (√2×√2)R45° reconstruction results from a rearrangement of the cation lattice in the outermost unit cell in which two octahedral cations are replaced by one tetrahedral interstitial, a motif conceptually similar to well-known Koch-Cohen defects in Fe (0001) is the most studied hematite surface, but 2 difficulties preparing stoichiometric surfaces under UHV conditions have hampered a definitive determination of the structure. There is evidence for at least three terminations: a bulk-like termination at the oxygen plane, a termination with half of the cation layer, and a termination with ferryl groups. When the surface is reduced the so-called "bi-phase" structure is formed, which eventually transforms to a Fe 3 O 4 (111)-like termination. The structure of the bi-phase surface is controversial; a largely accepted model of coexisting Fe 1-x O and α-Fe 2 O 3 (0001) islands was recently challenged and a new structure based on a thin film of Fe 3 O 4 (111) on α-Fe 2 O 3 (0001) was proposed. The merits of the compet...

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Section: Formic Acid (Hcooh)mentioning

confidence: 99%

Iron oxide surfaces

Parkinson

2016

Surface Science Reports

487

463

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“…The refractive indices of cytoplasm and nucleus are assumed to be 1.36 and 1.38, respectively, and the refractive indices of organelles uniformly distributed in the range of 1.40 ± 0.05 [6]. The dielectric functions for gold and Fe 3 O 4 are taken from the tabulated data measured by Johnson et al [18] and Schlegel et al [19], respectively.…”

Section: Cell Model and Parametersmentioning

confidence: 99%

Generalized multiparticle Mie modeling of light scattering by cells

et al. 2013

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The development of nanobiology requires a fundamental understanding of the interaction features between light and cells as well as cells containing nanoparticles. In this study, the generalized multiparticle Mie (GMM) theory was employed to calculate the scattering properties of cells under refractive index matching conditions. The angular distribution of scattered light is statistically averaged to obtain a good fit for the experimental results. Based on a simplified cell model, the variabilities between the scattered light pattern of normal cells and that of cancerous cells were examined. The results indicate that the small angle scattering is sensitive to the organelle distribution, which could be applied in the diagnostics of cancerous cells. Finally, the effects of cellular uptake of nanoparticles on the scattering pattern was also investigated.

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“…2. 22,23 Except for the weakest, all pump pulses heat the probed sample volume well above T V = 123 K. The residual peak intensity observed picoseconds after the pump pulse hence comes from a non-equilibrium transient phase.…”

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confidence: 96%

Time-resolved resonant soft x-ray diffraction with free-electron lasers: Femtosecond dynamics across the Verwey transition in magnetite

Pontius

Kachel

Schüßler-Langeheine

et al. 2011

Applied Physics Letters

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Resonant soft x-ray diffraction ͑RSXD͒ with femtosecond ͑fs͒ time resolution is a powerful tool for disentangling the interplay between different degrees of freedom in strongly correlated electron materials. It allows addressing the coupling of particular degrees of freedom upon an external selective perturbation, e.g., by an optical or infrared laser pulse. Here, we report a time-resolved RSXD experiment from the prototypical correlated electron material magnetite using soft x-ray pulses from the free-electron laser FLASH in Hamburg. We observe ultrafast melting of the charge-orbital order leading to the formation of a transient phase, which has not been observed in equilibrium. © 2011 American Institute of Physics. ͓doi:10.1063/1.3584855͔ Resonant x-ray diffraction, i.e., an x-ray diffraction experiment with the photon energy tuned into resonance with a dipole transition, combines the high spectroscopic sensitivity of x-ray absorption spectroscopy with momentum resolution. Thus it provides not only information on structural aspects of a material but also on its electronic properties. Particularly interesting in this regard are the strong dipole allowed excitations into transition-metal 3d, oxygen 2p, and lanthanide 4f-states, which all occur in the soft x-ray range between 400 and 1600 eV. Within the momentum space that can be probed with resonant soft x-ray diffraction are antiferromagnetic reflections from natural or artificial magnetic structures and superstructure reflections caused by periodic modulations of the electronic state as they occur in a large class of correlated electron systems. 1 A prototype material from the latter is magnetite ͑Fe 3 O 4 ͒. Already in the late 1930s Verwey discovered that upon lowering of the temperature below T V = 123 K ͑the Verwey temperature͒, magnetite undergoes a first-order phase transition leading to a conductivity decrease by two orders of magnitude. 2 This Verwey transition involves a change from a cubic inverse spinel high-temperature lattice structure to a complex monoclinic low-temperature phase. 3 Verwey proposed as the mechanism behind the drop in electrical conductivity a freezing of the charge fluctuations between octahedrally coordinated ͑B-site͒ Fe 2+ and Fe 3+ ions into a charge ordered structure. Calculations further predicted orbital order, i.e., a spatial modulation of the orbital occupation, for the low-temperature phase. 4-8 Both charge and orbital order have been observed experimentally, 3,6,9-11 even though no full consensus exists over all aspects of the order.One of the superstructure peaks characteristic of the lowtemperature phase is ͑0,0,1/2͒ ͑notation refers to the cubic room temperature unit cell with a = 8.39 Å͒. The inset to Fig. 1 shows a scan through this peak along the ͓001͔ ͑L͒ direction in reciprocal space. In the main panel of Fig. 1 the photon energy dependence of the ͑0,0,1/2͒-peak intensity ͑red͒ at the oxygen 1s → 2p ͑K͒ resonance is compared to the x-ray absorption spectrum ͑black͒ from the same sample. Since x-ray absorption p...

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Optical properties of magnetite (Fe₃O₄)

Cited by 208 publications

References 28 publications

Iron oxide surfaces

Iron oxide surfaces

Generalized multiparticle Mie modeling of light scattering by cells

Time-resolved resonant soft x-ray diffraction with free-electron lasers: Femtosecond dynamics across the Verwey transition in magnetite

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Optical properties of magnetite (Fe3O4)

Cited by 208 publications

References 28 publications

Iron oxide surfaces

Iron oxide surfaces

Generalized multiparticle Mie modeling of light scattering by cells

Time-resolved resonant soft x-ray diffraction with free-electron lasers: Femtosecond dynamics across the Verwey transition in magnetite

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Optical properties of magnetite (Fe₃O₄)