Crystal and magnetic structures of the brownmillerite compound Ca2Fe1.039(8)Mn0.962(8)O5

Ramezanipour, Farshid; Cowie, Bradley E.; Derakhshan, Shahab; Greedan, John E.; Cranswick, Lachlan M. D.

doi:10.1016/j.jssc.2008.10.010

Cited by 60 publications

(95 citation statements)

References 24 publications

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“…Following the results for Ca 2 FeMnO 5 , a full cation site ordering was assumed with Fe on the T site and Mn on the O site. 14 The refinement results for short r (to r = 5 Å) showed a significantly better agreement with the brownmillerite model, R w = 13.9%, compared to that for the disordered cubic model, R w = 19.7%. Therefore, the NPDF results suggest that, unlike the average structure, the local structure resembles an oxygen-ordered brownmillerite-type system with Fe mostly in a T site.…”

Section: Articlementioning

confidence: 83%

“…29 Given the strong O site preference of Mn 3+ found in Ca 2 FeMnO 5 ,Fe 3+ is expected to be found in T sites in disordered Sr 2 FeMnO 5 . 14 The room-temperature spectrum of Sr 2 FeMnO 5.5 (air; y = 0.5) is composed of two overlapping quadrupole doublets with essentially equal areas. This situation inevitably leads to two statistically equivalent models that cannot be distinguished on the basis of χ 2 alone, and the degeneracy can be lifted only by either ruling out one model on the basis of the fitted parameters or preparing a doped sample in which the 1:1 area ratio is changed.…”

Section: Articlementioning

confidence: 99%

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Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Ramezanipour¹,

Greedan²,

Siewenie

et al. 2011

Inorg. Chem.

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Local and average structures and magnetic properties of of Sr2FeMnO5+y, y = 0.0, 0.5. comparisons with Ca2FeMnO5 and the effect of the A-site cation Ramezanipour, Farshid; Greedan, John E.; Siewenie, Joan; Proffen, Th.; Ryan, Dominic H.; Grosvenor, Andrew P.; Donaberger, Ronald L.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. Oxygen-deficient perovskites can have a variety of structures depending on different factors including the degree of anion deficiency and the composition. In this article, the focus is on oxygen-deficient perovskites with the formula A 2 BB 0 O 5+x . The oxygen vacancies can order to form the brownmillerite structure in which the B cations are octahedrally coordinated, forming corner-sharing layers, and the B 0 cations are tetrahedrally coordinated, forming corner-sharing chains. (Figure 1). This longrange vacancy ordering results in a supercell that generally has dimensions with respect to the cubic perovskite cell constant, a p , of a br ≈ 2 1/2 a p , b br ≈ 4a p , and c br ≈ 2 1/2 a p . A number of different space group symmetries are observed, depending on subtle differences in the ordering of the tetrahedral chains within the unit cell. The chains can show either a right-handed (R) or lefthanded (L) orientation and the correlation between the intraand interlayer chain orientations and the resulting space groups are summarized in ABSTRACT: Sr 2 FeMnO 5+y was synthesized under two different conditions, in air and in argon, both of which resulted in a cubic, Pm3m, structure with no long-range ordering of oxygen vacancies. The unit cell constants were found to be a 0 = 3.89328(1) Å for argon (y = 0.0) and a 0 = 3.83075(3) Å for air (y = 0.5). In contrast, Ca 2 FeMnO 5 retains long-range brownmillerite oxygen vacancy ordering for either air or argon synthesis. Remarkably, Sr 2 FeMnO 5.0 oxidizes spontaneously in air at room temperature. A neutron pair distribution function (NPDF) study of Sr 2 FeMnO 5.0 (Ar) showed evidence for local, brownmillerite-like ordering of oxygen vacancies for short distances up to 5 Å. M€ ossbauer spectroscopy results indicate more than one Fe site for Sr 2 FeMnO 5+y (Ar and air), consistent with the noncubic local structure found by NPDF analysis. The isomer shifts and quadrupole splittings in both air-and argon-synthesized materials are consistent with the 3+ oxidation state for Fe in sites with coordination number four or five. This is confirmed by an L-edge XANES study. Mn is almost entirely in the 3+ state for Sr 2 FeMnO 5.0 (Ar), whereas Mn 4+ is predominantly present for Sr 2 FeMnO 5.5 (air). Magnetic susceptibility data show zero-fieldcooled/field-cooled (ZFC/FC) divergences near 50 K for the Ar sample and 25 K for the air sample, whereas Ca 2 FeMnO 5 is longrange G-type antiferromagnetically ordered at 407(2) K. Hyperfine magnetic splitting, observed in temperature-dependent M€ ossbauer measurements, indicates short-range magnetic correlations that persist up to 150 K for Sr 2 FeMnO 5.0 (Ar) and 100 K for Sr 2 FeMnO 5.5 (air), well above the ZF...

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Section: Articlementioning

confidence: 83%

Section: Articlementioning

confidence: 99%

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Ramezanipour¹,

Greedan²,

Siewenie

et al. 2011

Inorg. Chem.

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“…There are many examples of oxygen-deficient perovskites with other unusual physical properties, for example Ca 2 FeMnO 5 (Ramezanipour et al, 2009), Ca 2 MnAlO 5 (Wright et al, 2002), SrCaMnGaO 5+y (Battle et al, 2002), Ca 2 FeCoO 5 , Sr 2 Fe 1.9 M 0.1 O 5+ (where M = Mn, Cr, Co; = 0, 0.5), Sr 2 Fe 1.5 Cr 0.5 O 5 (Ramezanipour, 2011), and other perovskites with a brownmillerite-type ordering of oxygen vacancies (Anderson, Vaughey et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Anion order in perovskites: a group-theoretical analysis

2016

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Anion ordering in the structure of cubic perovskite has been investigated by the group-theoretical method. The possibility of the existence of 261 ordered low-symmetry structures, each with a unique space-group symmetry, is established. These results include five binary and 14 ternary anion superstructures. The 261 idealized anion-ordered perovskite structures are considered as aristotypes, giving rise to different derivatives. The structures of these derivatives are formed by tilting of BO6 octahedra, distortions caused by the cooperative Jahn-Teller effect and other physical effects. Some derivatives of aristotypes exist as real substances, and some as virtual ones. A classification of aristotypes of anion superstructures in perovskite is proposed: the AX class (the simultaneous ordering of A cations and anions in cubic perovskite structure), the BX class (the simultaneous ordering of B cations and anions) and the X class (the ordering of anions only in cubic perovskite structure). In most perovskites anion ordering is accompanied by cation ordering. Therefore, the main classes of anion order in perovskites are the AX and BX classes. The calculated structures of some anion superstructures are reported. Comparison of predictions and experimentally investigated anion superstructures shows coherency of theoretical and experimental results.

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“…[16][17][18] Determining the ratio of Fe to Mn at a specific crystal site can be difficult using X-ray diffraction because the atomic scattering factors of the metals are very similar. In contrast, the large difference in the scattering lengths of Fe and Mn in neutron diffraction enables clear observation of the selective B-site occupancies.…”

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Determination of Elemental Ratio in an Atomic Column by Electron Energy Loss Spectroscopy

et al. 2016

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Atomic-resolution quantification of the elemental ratio of Fe to Mn at the octahedral and tetrahedral sites in brownmillerite Ca2Fe1.07Mn0.93O5 was determined using electron energy-loss spectroscopy combined with aberration-corrected scanning transmission electron microscopy. The combined techniques revealed that oversampling of the spectral imaging data yielded a spatially resolved area that very nearly reflects atomic resolution (∼1.2 Å radius). The average experimental ratios of Fe to Mn within this region were 17.5:82.5 for the octahedral sites and 81.6:18.4 for the tetrahedral sites. The elemental ratio in an octahedral atomic column was successfully extracted by estimating the mixing of signals from nearest neighbor columns. The results indicated that the ratio of Fe to Mn was 13:87 at the octahedral site, which is in good agreement with the results of neutron diffraction analysis. In addition, the uncertainty of experimental results obtained by using an average 1.2 Å radius was less than 10% at octahedral sites, depending on the sample thickness. In contrast, the experimental error due to dechanneling of incident electrons was larger at the tetrahedral sites. This experimental procedure has wide application for determining the spatially resolved composition ratio of elements in perovskite-like compounds.

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Crystal and magnetic structures of the brownmillerite compound Ca2Fe1.039(8)Mn0.962(8)O5

Cited by 60 publications

References 24 publications

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Anion order in perovskites: a group-theoretical analysis

Determination of Elemental Ratio in an Atomic Column by Electron Energy Loss Spectroscopy

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Crystal and magnetic structures of the brownmillerite compound Ca2Fe1.039(8)Mn0.962(8)O5

Cited by 60 publications

References 24 publications

Local and Average Structures and Magnetic Properties of Sr2FeMnO5+y, y = 0.0, 0.5. Comparisons with Ca2FeMnO5 and the Effect of the A-Site Cation

Local and Average Structures and Magnetic Properties of Sr2FeMnO5+y, y = 0.0, 0.5. Comparisons with Ca2FeMnO5 and the Effect of the A-Site Cation

Anion order in perovskites: a group-theoretical analysis

Determination of Elemental Ratio in an Atomic Column by Electron Energy Loss Spectroscopy

Contact Info

Product

Resources

About

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation