Characterization of a natural magnetite

Doriguetto, Antônio C.; Fernandes, Nelson G.; Persiano, A. I. C.; Filho, E. Nunes; Grenèche, Jean‐Marc; Fabris, José Domingos

doi:10.1007/s00269-003-0310-x

Cited by 77 publications

(44 citation statements)

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“…A comparison of these Mössbauer parameters with weighted average values from ref. 75 and 77 suggests x > 0.95 for the Fe x O core, in agreement with EELS and X-ray results. The fitting results at T = 300 K indicate about 20% of Fe x O in the CS_45 particles, consistent also with the X-ray fits (ESI Table S2 †).…”

Section: Mössbauer Spectroscopysupporting

confidence: 87%

“…As shown in Table S2, † the obtained Mössbauer parameters are in reasonable agreement with previous studies on magnetite. 66,67,[73][74][75][76][77] Concerning the Fe x O subspectrum, it can be seen that at low temperatures (≤150 K, Fig. 8b-d) the high temperature paramagnetic peak opens into a resolved complex spectrum, indicating that the Fig.…”

Section: Mössbauer Spectroscopymentioning

confidence: 98%

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Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe_xO/Fe₃O₄nanoparticles as a case study

et al. 2015

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The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides.

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Section: Mössbauer Spectroscopysupporting

confidence: 87%

Section: Mössbauer Spectroscopymentioning

confidence: 98%

Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe_xO/Fe₃O₄nanoparticles as a case study

et al. 2015

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“…The mean values of the isomer shift δ, the hyperfine field B hyp , and those of the quadrupole splitting 2ε associated to all the species are listed in Table 2. The hyperfine field linked to the Fe 2+ ions is very similar to the value usually found for magnetite [15] for all the three composite samples. The value associated with Fe 3+ ions in the A and B sites, in contrast, was found larger than that for pure magnetite, [16] and smaller than that for CoFe 2 O 4 .…”

Section: Structure and Microstructuresupporting

confidence: 83%

Exchange‐Biased Fe₃₋_xO₄‐CoO Granular Composites of Different Morphologies Prepared by Seed‐Mediated Growth in Polyol: From Core–Shell to Multicore Embedded Structures

Franceschin

Gaudisson

Menguy

et al. 2018

Part & Part Syst Charact

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Magnetically contrasted granular hetero‐nanostructures are prepared by seed‐mediated growth in polyol, properly combining two oxide phases with different magnetic order, ferrimagnetic (F) partially oxidized magnetite Fe3−xO4 and antiferromagnetic (AF) cobalt oxide. Spinel Fe3−xO4 nanoparticles are first synthesized and then used as seeds for rock salt CoO nanocrystals growth. Three different hetero‐nanostructure designs are realized, acting on the content ratio between the seeds and the deposit's precursors during the synthesis. For all of them, the spinel and the rock salt phases are confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. Both phases are obtained in high‐crystalline quality with a net epitaxial relationship between the two crystallographic lattices. Mössbauer spectrometry confirms the cobalt cation diffusion into the spinel seeds, giving favorable chemical interfacing with the rock salt deposit, thus prevailing its heterogeneous nucleation and consequently offering the best condition for exchange‐bias (EB) onset. Magnetic measurements confirm EB features. The overall magnetic properties are found to be a complex interplay between dipolar interactions, exchange anisotropy at the F/AF interface, and magnetocrystalline anisotropy enhancement in the F phase, due to Co2+ diffusion into iron oxide's crystalline lattice. These results underline the powerfulness of colloidal chemistry for functional granular hetero‐nanostructured material processing.

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“…Abaixo da temperatura de Verwey (a temperatura em que a transição de fato ocorre depende da estequiometria da amostra 13,27,28 ), a estrutura do cristal muda de cúbica a monoclínica. É comumente difícil separar-se com segurança os efeitos magnéticos das duas transições, na interpretação do espectro Mössbauer da magnetita abaixo da Θ V , em virtude da complexidade da estrutura hiperfina 29,30 . Os espectros a 110 K (Figura 5), obtidos das frações magnéticas (FMPG e FMPI) dos materiais de areia deste estudo, revelam características espectrais mais claramente observáveis de que ocorreu a transição de Verwey.…”

Section: Resultsunclassified

Óxidos de ferro e monazita de areias de praias do Espírito Santo

Coelho¹,

Couceiro²,

Lopes³

et al. 2005

Quím. Nova

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IRON OXIDES AND MONAZITE FROM SANDS OF TWO BEACHES IN ESPIRITO SANTO, BRAZIL. Sand samples collected from two sampling sites on Guarapari and Iriri beaches, state of Espírito Santo, Brazil, were studied in an attempt to better describe their chemical and mineralogical compositions and radioactive behaviors. The sands were found to contain about 6 (Guarapari) and 2 dag kg-1 (Iriri) of rare earth and thorium that, if allocated to the monazite-(Ce) structure, lead to the averaged formulae

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Characterization of a natural magnetite

Cited by 77 publications

References 1 publication

Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe_xO/Fe₃O₄nanoparticles as a case study

Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe_xO/Fe₃O₄nanoparticles as a case study

Exchange‐Biased Fe₃₋_xO₄‐CoO Granular Composites of Different Morphologies Prepared by Seed‐Mediated Growth in Polyol: From Core–Shell to Multicore Embedded Structures

Óxidos de ferro e monazita de areias de praias do Espírito Santo

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Characterization of a natural magnetite

Cited by 77 publications

References 1 publication

Origin of the large dispersion of magnetic properties in nanostructured oxides: FexO/Fe3O4nanoparticles as a case study

Origin of the large dispersion of magnetic properties in nanostructured oxides: FexO/Fe3O4nanoparticles as a case study

Exchange‐Biased Fe3−xO4‐CoO Granular Composites of Different Morphologies Prepared by Seed‐Mediated Growth in Polyol: From Core–Shell to Multicore Embedded Structures

Óxidos de ferro e monazita de areias de praias do Espírito Santo

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Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe_xO/Fe₃O₄nanoparticles as a case study

Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe_xO/Fe₃O₄nanoparticles as a case study

Exchange‐Biased Fe₃₋_xO₄‐CoO Granular Composites of Different Morphologies Prepared by Seed‐Mediated Growth in Polyol: From Core–Shell to Multicore Embedded Structures