Cation distribution and structure modelling of spinel solid solutions

Lavina, Barbara; Salviulo, Gabriella; Giusta, A. Della

doi:10.1007/s002690100198

Cited by 148 publications

(127 citation statements)

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“…Recent work 22 has confirmed that Ti 4 þ almost always goes into the octahedral site 12 when it is the only non-Fe cation, but it is well known that Mg 2 þ will partition into either site 31 . Although Al 3 þ has a relatively strong preference for the octahedral site, it is not uncommon to find it in the tetrahedral site, and even less is known about site preference or valence state of Mn 35 . Site vacancies add another layer of uncertainty to the problem, though Wanamaker and Moskowitz 11 have shown and Lattard et al 15 have confirmed that higher numbers of cation vacancies appear to result in a more disordered cation distribution.…”

Section: Discussionmentioning

confidence: 99%

Inferred time- and temperature-dependent cation ordering in natural titanomagnetites

et al. 2013

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Despite years of efforts to quantify cation distribution as a function of composition in the magnetite-ulvöspinel solid solution, important uncertainties remain about the dependence of cation ordering on temperature and cooling rate. Here we demonstrate that Curie temperature in a set of natural titanomagnetites (with some Mg and Al substitution) is strongly influenced by prior thermal history at temperatures just above or below Curie temperature. Annealing for 10 À 1 to 10 3 h at 350-400°C produces large and reversible changes in Curie temperature (up to 150°C). By ruling out oxidation/reduction and compositional unmixing, we infer that the variation in Curie temperature arises from cation reordering, and Mössbauer spectroscopy supports this interpretation. Curie temperature is therefore an inaccurate proxy for composition in many natural titanomagnetites, but the cation reordering process may provide a means of constraining thermal histories of titanomagnetite-bearing rocks. Further, our theoretical understanding of thermoremanence requires fundamental revision when Curie temperature is itself a function of thermal history.

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Section: Discussionmentioning

confidence: 99%

Inferred time- and temperature-dependent cation ordering in natural titanomagnetites

et al. 2013

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“…Several different procedures may be adopted to determine cation distribution [47,48], and satisfying results can generally be obtained by combining data from single-crystal X-ray structural refinements and electron microprobe analyses. This approach simultaneously takes into account both the structural and chemical data and reproduces the observed parameters by optimizing cation distributions.…”

Section: Cation Distributionmentioning

confidence: 99%

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

et al. 2018

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Abstract:We investigated the crystal and structural behavior of several Cr-bearing spinels from the Archean chromitites of Amsaga (Mauritania). The chemical and structural data testified a retrograde metamorphism from amphibolite to greenschist facies, witnessed by relative changes in the amount of all the major oxides (Cr, Al, Mg, Fe 2+ , Fe 3+ ), the relative proportion of Fe 3+ /Fe tot as well as the structural parameters, including the cell edge and the oxygen coordinate. The general agreement between electron microprobe and Mössbauer data indicates that the analyzed spinels are stoichiometric. The structural data revealed that the oxygen positional parameter of amphibole-bearing samples is the highest observed among Cr-bearing spinels with similar Cr# and Mg#. Consequently, it is suggested that a structural study of detrital Cr-spinels could be important in discriminating an amphibole-chromitite source from an ophiolite source.

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“…given the strong preference of the Cr for octahedral sites in spinels as compared to Co. 24,25 A comparison between spectra 2 (SCF sample) and 4 (CFO crystal) suggest that the room temperature XMCD for the CCO bilayer is a superposition of an octahedral Co 2+ contribution from the interface region and a much smaller signal from tetrahedral Co 2+ in bulk-like CCO. Based on the tetrahedral- (SC and CCO target) and Co…”

Section: +mentioning

confidence: 99%

Magnetism at spinel thin film interfaces probed through soft X-ray spectroscopy techniques

Chopdekar

Liberati

Takamura

et al. 2010

Journal of Magnetism and Magnetic Materials

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Magnetic order and coupling at the interfaces of highly spin polarized Fe3O4 heterostructures have been determined by surface sensitive and element specific soft x-ray spectroscopy and spectromicroscopy techniques. At ambient temperature, the interface between paramagnetic CoCr2O4 or MnCr2O4 and ferrimagnetic Fe3O4 isostructural bilayers exhibits long range magnetic order of Co, Mn and Cr cations which cannot be explained in terms of the formation of interfacial MnFe2O4 or CoFe2O4. Instead, the ferrimagnetism is induced by the adjacent Fe3O4 layer and is the result of the stabilization of a spinel phase not achievable in bulk form. Magnetism at the interface region is observable up to 500 K, far beyond the chromite bulk Curie temperature of 50-95 K.

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Cation distribution and structure modelling of spinel solid solutions

Cited by 148 publications

References 0 publications

Inferred time- and temperature-dependent cation ordering in natural titanomagnetites

Inferred time- and temperature-dependent cation ordering in natural titanomagnetites

Following the Amphibolite to Greenschist Metamorphic Path through the Structural Parameters of Spinels from Amsaga (Mauritania)

Magnetism at spinel thin film interfaces probed through soft X-ray spectroscopy techniques

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