XAFS study on site occupation of cobalt and iron in Z-type ferrite, Ba3Co2−xFe24+xO41

Nakagawa, Takashi; Yuya, Masato; Tachibana, Takeshi; Takada, Yoko; Nitani, Hiroaki; Emura, S.; Yamamoto, Takao A.

doi:10.1016/j.jmmm.2004.09.121

Cited by 20 publications

(10 citation statements)

References 6 publications

(6 reference statements)

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“…Moreover, EXAFS has been recently found to be a useful tool to determine the cation distribution in ferrite spinels. [23][24][25] In the structure of ferrites, cations (bivalent and trivalent) reside on the tetrahedral and octahedral sites available in the close packing of oxygen anions. The cation distribution is defined by the inversion parameter i which indicates the fraction of trivalent cations in tetrahedral sites.…”

Section: Introductionmentioning

confidence: 99%

Formation and cation distribution in supported manganese ferrite nanoparticles: an X-ray absorption study

Carta

Casula

Mountjoy

et al. 2008

Phys. Chem. Chem. Phys.

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Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) techniques at both Fe and Mn K-edges were used to investigate the formation of MnFe(2)O(4) nanoparticles embedded in a silica aerogel matrix as a function of calcination temperature (at 450, 750 and 900 degrees C). Up to 450 degrees C, two separated highly-disordered phases of iron and manganese are present. With increasing the temperature (to 750 and 900 degrees C), the structure of aerogel nanoparticles becomes progressively similar to that of the spinel structure MnFe(2)O(4) (jacobsite). Quantitative determination of cations distribution in the spinel structure shows that aerogels calcined at 750 and 900 degrees C have a degree of inversion i = 0.20. A pure jacobsite sample synthesised by co-precipitation and used as a reference compound shows a much higher degree of inversion (i = 0.70). The different distribution of iron and manganese cations in the octahedral and tetrahedral sites in pure jacobsite and in the aerogels can be ascribed to partial oxidation of Mn(2+) to Mn(3+) in pure jacobsite, confirmed by XANES analysis, probably due to the synthesis conditions.

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Section: Introductionmentioning

confidence: 99%

Formation and cation distribution in supported manganese ferrite nanoparticles: an X-ray absorption study

Carta

Casula

Mountjoy

et al. 2008

Phys. Chem. Chem. Phys.

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“…EXAFS gives information about bond distances and coordination numbers of shells surrounding the absorbing atom; XANES gives information on the symmetry and oxidation state of the absorbing atom. Moreover, EXAFS has recently been found to be a useful tool to determine the cation distribution in ferrospinels. , In the structure of ferrites, cations (bivalent and trivalent) reside on the tetrahedral and octahedral sites available in the close packing of oxygen anions. The cation distribution between octahedral and tetrahedral sites can vary and crucially influences the catalytic, magnetic, and electronic properties.…”

Section: Introductionmentioning

confidence: 99%

X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

et al. 2007

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X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) techniques at both Fe and Co K-edges were used to investigate the formation of CoFe 2 O 4 nanoparticles embedded in a silica aerogel matrix as a function of calcination temperature and CoFe 2 O 4 content. In particular, nanocomposite aerogels containing relative CoFe 2 O 4 amounts of 5 and 10 wt % and calcined at 450, 750, and 900°C were studied. The evolution of the nanophase with calcination temperatures depends on the composition. In the sample containing 10 wt % of nanophase, results indicate that CoFe 2 O 4 nanocrystals were formed after calcination at 750°C, whereas in the sample containing 5 wt % of nanophase, they were obtained only after calcination at 900°C. Quantitative determination of the distribution of the iron and cobalt phase in the octahedral and tetrahedral sites of the spinel structure shows that cobalt ferrite prepared by sol-gel has a partially inverted spinel structure with a degree of inversion around 0.70.

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“…Figure 7 shows the occupation numbers of cobalt ions over various sites in the Z-type crystal structure determined from the pattern measured at 773 K, which shows that cobalt ions are exclusively located only at five sites, Me1(2a), Me4(12k), Me5(4e), Me8(12k) and Me10(2d), out of the ten available sites. 10,11) Although we reported in the previous paper 8,9) that not five but four sites accommodate cobalt, the results from HERMES and the measurements with HRPD should be more reliable because of their higher resolutions. 19) Note that the circumstances of the Me4 sites are almost the same as those of the Me8 sites.…”

Section: Resultsmentioning

confidence: 80%

Temperature Dependence of Magnetic Moment Orientation in Co₂Z-Type Hexaferrite Estimated by High-Temperature Neutron Diffraction

Takada¹,

Nakagawa²,

Fukuta³

et al. 2005

Jpn. J. Appl. Phys.

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We investigated the correlation between the thermomagnetic curve of Co 2 Z-type hexagonal barium ferrite and its magnetic moment direction. We measured the thermomagnetic curve of Ba 3 Co 1:8 Fe 24:2 O 41 , prepared using the conventional solid-state reaction method, in the temperature range from 294 to 773 K with a vibrating sample magnetometer under 70 Oe. The curve shows two significant magnetization slumps at 540 K and 680 K. High-temperature XRD patterns show that no crystal transformation occurs in the temperature region from 294 to 773 K. High-temperature neutron diffraction experiments were performed to investigate the magnetic moment orientation at elevated temperatures. The Rietveld analyses of the neutron diffraction patterns indicate that the temperature rise from 523 to 573 K makes the magnetic moments turn to the c-axis from a direction parallel to the c-plane most significantly. The slump in magnetization at 540 K may be attributed to the change in easy magnetization direction from the c-plane to the c-axis. The change in average orientation of the magnetic moments must be induced by the disappearance of the contribution of cobalt to magnetism in this temperature range.

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XAFS study on site occupation of cobalt and iron in Z-type ferrite, Ba3Co2−xFe24+xO41

Cited by 20 publications

References 6 publications

Formation and cation distribution in supported manganese ferrite nanoparticles: an X-ray absorption study

Formation and cation distribution in supported manganese ferrite nanoparticles: an X-ray absorption study

X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

Temperature Dependence of Magnetic Moment Orientation in Co₂Z-Type Hexaferrite Estimated by High-Temperature Neutron Diffraction

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XAFS study on site occupation of cobalt and iron in Z-type ferrite, Ba3Co2−xFe24+xO41

Cited by 20 publications

References 6 publications

Formation and cation distribution in supported manganese ferrite nanoparticles: an X-ray absorption study

Formation and cation distribution in supported manganese ferrite nanoparticles: an X-ray absorption study

X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

Temperature Dependence of Magnetic Moment Orientation in Co2Z-Type Hexaferrite Estimated by High-Temperature Neutron Diffraction

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Temperature Dependence of Magnetic Moment Orientation in Co₂Z-Type Hexaferrite Estimated by High-Temperature Neutron Diffraction