Electronic and magnetic properties of ultra-thin epitaxial magnetite films on MgO(001)

Zając, M.; Freindl, K.; Ślęzak, T.; Ślęzak, M.; Spiridis, N.; Wilgocka-Ślęzak, D.; Korecki, J.

doi:10.1016/j.tsf.2011.03.037

Cited by 22 publications

(20 citation statements)

References 47 publications

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“…Although 295 K data were collected for all samples, they were not useful because some of the Fe oxides were too fine‐grained to be magnetically ordered at that temperature. Such superparamagnetism has been observed in both biogenic and synthetic magnetite at particle sizes below ~13 nm, often manifested as a doublet in room temperature Mössbauer spectra (Hassett et al ., ; Vali et al ., ; Weiss et al ., ; Ambashta et al ., ; Kalska‐Szostko et al ., ; Bandhu et al ., ; Li et al ., ; Marquez‐Linares et al ., ; Starowicz et al ., ; Zając et al ., ). The magnetic field of superparamagnetic nanoparticles varies in direction faster than the inverse lifetime of the 57 Fe nuclear excited state (on the order of 10 7 s −1 ).…”

Section: Methodsmentioning

confidence: 97%

Magnetite formation from ferrihydrite by hyperthermophilic archaea from Endeavour Segment, Juan de Fuca Ridge hydrothermal vent chimneys

et al. 2014

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Hyperthermophilic iron reducers are common in hydrothermal chimneys found along the Endeavour Segment in the northeastern Pacific Ocean based on culture-dependent estimates. However, information on the availability of Fe(III) (oxyhydr) oxides within these chimneys, the types of Fe(III) (oxyhydr) oxides utilized by the organisms, rates and environmental constraints of hyperthermophilic iron reduction, and mineral end products is needed to determine their biogeochemical significance and are addressed in this study. Thin-section petrography on the interior of a hydrothermal chimney from the Dante edifice at Endeavour showed a thin coat of Fe(III) (oxyhydr) oxide associated with amorphous silica on the exposed outer surfaces of pyrrhotite, sphalerite, and chalcopyrite in pore spaces, along with anhydrite precipitation in the pores that is indicative of seawater ingress. The iron sulfide minerals were likely oxidized to Fe(III) (oxyhydr) oxide with increasing pH and Eh due to cooling and seawater exposure, providing reactants for bioreduction. Culture-dependent estimates of hyperthermophilic iron reducer abundances in this sample were 1740 and 10 cells per gram (dry weight) of material from the outer surface and the marcasite-sphalerite-rich interior, respectively. Two hyperthermophilic iron reducers, Hyperthermus sp. Ro04 and Pyrodictium sp. Su06, were isolated from other active hydrothermal chimneys on the Endeavour Segment. Strain Ro04 is a neutrophilic (pH opt 7-8) heterotroph, while strain Su06 is a mildly acidophilic (pH opt 5), hydrogenotrophic autotroph, both with optimal growth temperatures of 90-92 °C. Mössbauer spectroscopy of the iron oxides before and after growth demonstrated that both organisms form nanophase (<12 nm) magnetite [Fe3 O4 ] from laboratory-synthesized ferrihydrite [Fe10 O14 (OH)2 ] with no detectable mineral intermediates. They produced up to 40 mm Fe(2+) in a growth-dependent manner, while all abiotic and biotic controls produced <3 mm Fe(2+) . Hyperthermophilic iron reducers may have a growth advantage over other hyperthermophiles in hydrothermal systems that are mildly acidic where mineral weathering at increased temperatures occurs.

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Section: Methodsmentioning

confidence: 97%

Magnetite formation from ferrihydrite by hyperthermophilic archaea from Endeavour Segment, Juan de Fuca Ridge hydrothermal vent chimneys

et al. 2014

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“…The reduced thickness is also reflected in the reduced Curie temperature [32], which in turn produces smaller value of the local magnetization (measured by the hyperfine magnetic field). Also superparamagnetism plays an essential role in blurring the Mössbauer spectra, as it was demonstrated recently for Fe 3 O 4 (001) films thinner than 5 nm [7]. The superparamagnetic relaxation is blocked by lowering the temperature, and the CEMS spectra at cryogenic temperatures reveal typical features of magnetite (an example for a 2 PML film is shown in the inset of Fig.…”

Section: Methodsmentioning

confidence: 60%

“…Grown on different substrates and by various methods, magnetite thin films have been widely described in the literature (for recent literature references, consult Refs. [6,7,8]). Many of these studies have focused on magnetite films grown on MgO(001) surfaces by the reactive deposition of iron in the atmosphere of molecular oxygen, which predominantly leads to the stabilization of (001)-oriented Fe 3 O 4 films.…”

Section: Introductionmentioning

confidence: 99%

“…Apparently, polarity compensation does not influence the epitaxial growth, and flat and continuous (001)-oriented magnetite films can be epitaxially grown without thickness limitation [12,13]. This system, however, exhibits undesirable magnetic properties associated with structural defects (anti-phase domain boundaries), such as superparamagnetism [14,7] and very high saturation field [15].…”

Section: Introductionmentioning

confidence: 99%

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Growth and electronic and magnetic structure of iron oxide films on Pt(111)

et al. 2012

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Ultrathin (111)-oriented polar iron oxide films were grown on a Pt(111) single crystal either by the reactive deposition of iron or oxidation of metallic iron monolayers. These films were characterized using low energy electron diffraction, scanning tunneling microscopy and conversion electron Mossbauer spectroscopy. The reactive deposition of Fe led to the island growth of Fe 3 O 4 , in which the electronic and magnetic properties of the bulk material were modulated by superparamagnetic size effects for thicknesses below 2 nm, revealing specific surface and interface features. In contrast, the oxide films with FeO stoichiometry, which could be stabilized as thick as 4 nm under special preparation conditions, had electronic and magnetic properties that were very different from their bulk counterpart, wüstite. Unusual long range magnetic order appeared at room temperature for thicknesses between three and ten monolayers, the appearance of which requires severe structural modification from the rock-salt structure. PACS: 68.47.Gh Oxide surfaces, 68.55.-a Thin film structure and morphology, 75.70.Ak Magnetic properties of monolayers and thin films, 81.15.-z Methods of deposition of films and coatings; film growth and epitaxy, 82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

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“…In the second example [22], the film was prepared in UHV system containing a miniature molecular beam epitaxy system equipped with metal vapor sources, quartz thickness monitors, and a four-grid low-energy electron diffraction/Auger electron spectroscopy (LEED/AES) spectrometer to monitor thickness and composition. In both cases, the thin films were used to carefully study the magnetic properties of a 2D system, correlating the magnetic features with their thickness and establishing the limits of the material for application ( Fig.…”

Section: Thin Filmsmentioning

confidence: 99%