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Shepherd, J.; Koenitzer, J. W.; Aragón, R.; Sandberg, C. J.; Honig, J. M.

doi:10.1103/physrevb.31.1107

Cited by 79 publications

(38 citation statements)

References 35 publications

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“…It is generally accepted that the presence of Verwey transition is very sensitive to the stoichiometry and homogeneity of magnetite thin films. 18 The temperature (T V ) at which such a transition occurs has been commonly observed to decrease from the bulk value down to 85K and could even disappear with the decreasing Fe 3 O 4 thicknesse. 11,19,20,21,38 The observed transition temperature of the 12nm Fe 3 O 4 /MgO(100) thin film in this study agrees well with the reported T V of the magnetite films on or near stoichiometry, 11,22 suggesting the sample is not overly suffering from cation or anion vacancies.…”

Section: Sample Preparation and Global Characterizationmentioning

confidence: 99%

X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

Liu

Song

Maltby

et al. 2015

Journal of Applied Physics

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Abstract:The spin and orbital magnetic moments of the Fe 3 O 4 epitaxial ultrathin film synthesized by plasma assisted simultaneous oxidization on MgO(100) have been studied with X-ray magnetic circular dichroism (XMCD). The ultrathin film retains a rather large total magnetic moment, i.e. (2.73±0.15)μ B /f.u., which is ~ 70% of that for the bulk-like Fe 3 O 4 . A significant unquenched orbital moment up to (0.54±0.05) μ B /f.u. was observed, which could come from the symmetry breaking at the Fe 3 O 4 /MgO interface. Such sizable orbital moment will add capacities to the Fe 3 O 4 -based spintronics devices in the magnetization reversal by the electric field.

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Section: Sample Preparation and Global Characterizationmentioning

confidence: 99%

X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

Liu

Song

Maltby

et al. 2015

Journal of Applied Physics

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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.…”

mentioning

confidence: 99%

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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“…In Fig. 9a and 9b are shown examples of resistivity changes near the Verwey transition temperature for zinc ferrites samples of composition Fe3"Zn"O4 i and for the titanomagnetite series Fe3_ y Tiy O4 [21]. With increasing 8, x, or y there are striking alterations in the nature of the Verwey transformation: it changes from first order to higher order and ultimately disappears.…”

Section: The Magnetite Titanomagnetite and Zinc Ferrite Systemmentioning

confidence: 99%

“…Circles represent experimental data cited in Ref. [21]. As is well established, as long as the kinetic contributions to a is small, as is the case for nearly localized carriers α = -μ E/kBT, where µE = (8Fb/8γ2)τ -E is the chemical potential relative to the transport level at energies E above the ground state εCA .…”

Section: The Magnetite Titanomagnetite and Zinc Ferrite Systemmentioning

confidence: 99%

“…Most of the early work is superseded by the recent recognition [21] that small changes in the oxygen to metal ratio, represented by δ in the formula Fe3(½_004 (-0.0005 < 6 < 0.012), completely alter the characteristics of the material. Figures 7 and 8 display typical changes in heat capacity and electrical resistivity pc encountered in specimens of different compositions 6.…”

Section: The Magnetite Titanomagnetite and Zinc Ferrite Systemmentioning

confidence: 99%

See 1 more Smart Citation

Electron Correlation Phenomena in Selected Transition Metal Oxides

Honig

1994

Acta Phys. Pol. A

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The theory of electron correlation phenomena is reviewed and used to interpret the transport, thermal, or magnetic properties of V203, LaNiO3 and Fe304 systems, each of which to a greater or lesser degree displays correlation effects. A rationale is provided for interpreting the various types of phase transitions encountered in the vanadium sesquioxide and magnetite host systems and to show why these are altered by small compositional variations.

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Heat capacity studies on single crystal annealedFe3O4

Cited by 79 publications

References 35 publications

X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

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

Electron Correlation Phenomena in Selected Transition Metal Oxides

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