Effect of stoichiometry changes on electrical properties of magnetite

Aragón, R.; Rasmussen, R. J.; Shepherd, J.; Koenitzer, J. W.; Honig, J. M.

doi:10.1016/0304-8853(86)90844-9

Cited by 63 publications

(24 citation statements)

References 8 publications

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“…The latter orbital is characterized by a very strong anisotropy of the charge and spin distribution, with the angular part stretched along the hexagonal c axis. This is 57 Fe, which is negatively proportional to the increase in the s-electron density at the Fe nucleus, usually follows a volume reduction (see Ref. [34]).…”

Section: A Case Of a Mott Transition Driven By An Increasing Crystal-mentioning

confidence: 99%

“…At ambient pressure the spins are highly frustrated between neighboring layers as well as within layers [39]. The combined high-pressure studies of CuFeO 2 using X-ray diffraction, along with 57 Fe Mössbauer and Fe and CuK-edge XAFS spectroscopy methods [40], reveal a sequence of intricate structural/electronic-magnetic pressure-induced transitions. At 18 GPa a structural transition takes place to a more isotropic C2/c structure (HP1) with the O-Cu 1þ S¼0 -O axis tilted 28°from the c axis (Fig.…”

Section: A Case Of Pressure-induced Intervalence Charge Transfermentioning

confidence: 99%

“…This observation drastically contradicts with the P-T diagram obtained using a cubic-anvil device [55] or soft noble gases as the pressure medium [56], in which the role of stresses is significantly reduced. It is noteworthy that the Verwey transition in magnetite is extremely sensitive not only to the stress but also to the oxygen stoichiometry [57] and this aspect should be taken into account in the synthesis procedure. With reference to the phenomena particularly discussed in the present paper, non-hydrostaticity and significant pressure gradients could be an additional reason (see footnote 1) of the often observed discrepancy between the values of the transition pressure obtained in XRD, MS and R(P, T) experiments.…”

Section: Fig 12mentioning

confidence: 99%

“…All the above mentioned electronic transitions corroborate as a rule with appreciable structural transformations being either a cause or a consequence of the latter. This paper focuses on the above-mentioned topics emanating primarily from our previous experimental investigations employing the following high-pressure methodologies: (i) diamond anvil cells (DACs) capable of generating static pressures beyond 100 GPa, (ii) X-ray diffraction (XRD) to characterize crystal structures and interatomic distances, (iii) 57 Fe Mössbauer spectroscopy (MS), a magnetic probe to document the in-situ magnetic/electronic transitions, (iv) electrical resistance to quantify electronic mobility and detect the insulator-metal transitions; and (v) X-ray absorption spectroscopy (XAS) to study valence and coordination changes in Fe and corresponding TM constituents. Although HP-MS is limited to Fe-containing TMC, the principles governing electron-and spin-correlation effects can be probed in a coherent fashion, and in support of a deeper theoretical understanding.…”

Section: Introductionmentioning

confidence: 99%

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The Mott insulators at extreme conditions; structural consequences of pressure-induced electronic transitions

Rozenberg

Pasternak

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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Electronic/magnetic transitions and their structural consequences in Fe-based Mott insulators in a regime of very high static density are the main issue of this short review paper. The paper focuses on the above-mentioned topics based primarily on our previous and ongoing experimental HP studies employing: (i) diamond anvil cells, (ii) synchrotron X-ray diffraction, (iii) 57 FeMössbauer spectroscopy, (iv) electrical resistance and (v) X-ray absorption spectroscopy. It is shown that applying pressure to such strongly correlated systems leads to a number of changes; including quenching of the orbital moment, quenching of Jahn-Teller distortion, spin crossover, inter-valence charge transfer, insulator-metal transition, moment collapse and volume collapse. These changes may occur simultaneously or sequentially over a range of pressures. Any of these may be accompanied by or be a consequence of a structural phase transition; namely, a change in crystal symmetry. Analyzing this rich variety of phenomena we show the main scenarios which such strongly correlated systems may undergo on the way to a correlation breakdown (Mott transition

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Section: A Case Of a Mott Transition Driven By An Increasing Crystal-mentioning

confidence: 99%

Section: A Case Of Pressure-induced Intervalence Charge Transfermentioning

confidence: 99%

Section: Fig 12mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Mott insulators at extreme conditions; structural consequences of pressure-induced electronic transitions

Rozenberg

Pasternak

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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“…The Verwey transition temperature (T V ) was found to be (122 ± 1) K [46]. Stoichiometric magnetite is expected to have a T V of around 120 K [47]. As magnetite becomes cation deficient T V decreases, and the transition eventually disappears.…”

Section: Methodsmentioning

confidence: 99%

Oxygen vacancy induced surface stabilization: (110) terminated magnetite

et al. 2016

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Scanning tunneling microscopy (STM) measurements of the (110) surface of magnetite showed the coexistence of two reconstructions: the known (1 × 3) row reconstruction and a surprising atomic structure of high complexity which occupies a small fraction of the surface. Oxygen vacancies on the Fe3O4(110) B-terminated surface have previously been determined to be the most energetically favourable surface termination of those considered [Li et al., Surf. Sci. 601, 876 (2007)]. However, this study only investigated oxygen vacancies which were three-fold coordinated. Here, first principle calculations indicate that two-fold coordinated oxygen represents the most energetically stable oxygen vacancy on the B-terminated (110) surface of magnetite. STM simulations reveal that the structure that occupies a small fraction of the surface corresponds to this energetically favourable B-terminated Fe3O4(110) surface. The oxygen vacancies form an ordered array: along the [110] direction, every second two-fold coordinated oxygen atom is vacant, vacancies are separated by 6Å. In adjacent two-fold coordinated oxygen rows, the vacancies are shifted in the [110] direction by 3Å. Density functional theory (DFT) calculations of the spin density distributions indicate that surface and sub-surface octahedrally coordinated iron atoms are charge ordered. The charge ordering and existence of oxygen vacancies act to reduce the surface charge. However, other polarity compensation mechanisms may be at play to stabilize the surface.

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Atomic scale spin‐dependent STM on magnetite using antiferromagnetic STM tips

Murphy

Ceballos

Mariotto

et al. 2005

Microscopy Res & Technique

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STM tips made from antiferromagnetic MnNi have been used to investigate the atomic structure of the (001) and (111) surfaces of Fe 3 O 4 . The clean (001) surface displays a (√2 × √2)R45° superlattice, which is attributed to charge-ordering on the surface, where Fe 2+ -Fe 2+ and Fe 3+ -Fe 3+ dimers can be discriminated. The oxygenterminated (111) surface is characterized by an hexagonal superlattice with a periodicity of 42 Å. Oxygen vacancies are observed in atomically resolved images of this superlattice. In the presence of an external magnetic field of 60 mT, a significant change in the atomic corrugation in the topmost oxygen layer around each of these defects is observed. The results on both (001) and (111) surfaces are discussed in terms of possible spin polarized effects.

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Effect of stoichiometry changes on electrical properties of magnetite

Cited by 63 publications

References 8 publications

The Mott insulators at extreme conditions; structural consequences of pressure-induced electronic transitions

The Mott insulators at extreme conditions; structural consequences of pressure-induced electronic transitions

Oxygen vacancy induced surface stabilization: (110) terminated magnetite

Atomic scale spin‐dependent STM on magnetite using antiferromagnetic STM tips

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