Electronic structure and hyperfine fields in non-stoichiometric magnetite above the Verwey transition

Chlan, V.; Novák, P.; Štěpánková, H.; Řezníček, R.; Kouřil, Karel; Kozłowski, A.

doi:10.1016/j.jmmm.2009.03.026

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…4 frequencies of pronounced peaks in the spectra of nanoparticle sample are plotted as functions of temperature. The dependences closely match those of spectral lines of stoichiometric magnetite [1,7] and main lines and satellite lines S1, S2, and S3 in spectra of nonstoichiometric magnetite, where the satellite lines are induced by vacancies at octahedral (B) sites [8]. Moreover, a good correspondence with temperature dependences of 57 Fe NMR signals of maghemite [4] is also found.…”

Section: Discussionsupporting

confidence: 64%

Structure of Iron Oxide Nanoparticles Studied by ^{57}Fe NMR

et al. 2014

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In this work we apply nuclear magnetic resonance (NMR) spectroscopy of 57 Fe nuclei for investigation of submicron and nanocrystalline iron oxide systems. The studied iron oxide particles are obtained from ferrous hydroxide gels (prepared from FeCl2 and KOH) by aging at elevated temperatures (90 • C) with KNO3 as oxidant. The 57 Fe NMR spectra of the samples are measured in temperature range 4.2370 K in a zero external magnetic eld. Signals of 57 Fe nuclei assigned to tetrahedral and octahedral iron sites are well resolved. The NMR spectra and their temperature dependences are compared with those of stoichiometric and nonstoichiometric magnetite single crystals, as well as with samples of maghemite.

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Section: Discussionsupporting

confidence: 64%

Structure of Iron Oxide Nanoparticles Studied by ^{57}Fe NMR

et al. 2014

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“…Namely, while few O vacancies are admitted, the most common defects are Fe B vacancies, whose existence is known to preserve a first-order VT up to significant concentrations [101][102][103][104]. However, the inhomogeneities in the sample composition break the continuity of the longrange order required for the VT, broadening the features of the transition and reducing the value of T V [103,105,106]. All these effects are common to bulk samples and films [87].…”

Section: Magnetite Thin Filmsmentioning

confidence: 99%

Electronic phase transitions in ultrathin magnetite films

Bernal-Villamil

Gallego

2015

J. Phys.: Condens. Matter

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Magnetite (Fe3O4) shows singular electronic and magnetic properties, resulting from complex electron-electron and electron-phonon interactions that involve the interplay of charge, orbital and spin degrees of freedom. The Verwey transition is a manifestation of these interactions, with a puzzling connection between the low temperature charge ordered state and the dynamic charge fluctuations still present above the transition temperature. Here we explore how these rich physical phenomena are affected by thin film geometries, particularly focusing on the ultimate size limit defined by thicknesses below the minimum bulk unit cell. On one hand, we address the influence of extended defects, such as surfaces or antiphase domains, on the novel features exhibited by thin films. On the other, we try to isolate the effect of the reduced thickness on the electronic and magnetic properties. We will show that a distinct phase diagram and novel charge distributions emerge under reduced dimensions, while holding the local high magnetic moments. Altogether, thin film geometries offer unique possibilities to understand the complex interplay of short- and long-range orders in the Verwey transition. Furthermore, they arise as interesting candidates for the exploitation of the rich physics of magnetite in devices that demand nanoscale geometries, additionally offering novel functionalities based on their distinct properties with respect to the bulk form.

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“…[9][10][11] All the possible explanations must be considered successively to identify the genuine reason for these bad performances and to break the deadlocks standing in the way of magnetite-based devices. Several studies focused on the modification of the physical properties of magnetite induced by structural defects like antiphase boundaries [12][13][14][15] and cationic vacancies 16,17 or by interfaces with an insulating barrier. 18,19 We propose to study a new scenario to explain the low performances of magnetite-based devices, namely the modification of the electronic structure induced by oxygen vacancies in this oxide.…”

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confidence: 99%