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  • 1
    Electronic Resource
    Electronic Resource
    Structural features of the La-Sr-Fe-Co-O system (2001)
    Springer
    The European physical journal 21 (2001), S. 521-526 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Vn Colossal magnetoresistance – 61.72.-y Defects and impurities in crystals; microstructure – 72.15.Gd Galvanomagnetic and other magnetotransport effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A structural study has been performed on the La0.8Sr0.2FexCo1-xO3 (x = 0.025 to 0.3) system displaying large magnetoresistance (MR) at room temperature. A detailed analysis of the crystal structure and microstructure was done by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM). The atomic resolution TEM images and the appearing superreflections in the corresponding SAED patterns revealed that a superstructure is formed due to the presence of iron. The correlation between the ordered microstructure and the observed large MR ratio is discussed. 57Fe Mössbauer spectroscopy was utilized to gain information on the valence state of iron in the sample with x = 0.3. The lattice parameters of Fe- doped La0.8Sr0.2FexCo1-xO3 compounds were found to increase monotonously with increasing Fe content. The valence state of iron was found to be Fe3+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011125
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  • 2
    Electronic Resource
    Electronic Resource
    Study of (Ln,Sr)(Fe,Co)O〈sub〉3-δ〈/sub〉 Type CMR Materials by 〈sup〉57〈/sup〉Co Emission Mössbauer Spectroscopy (2003)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 90-91 (Apr. 2003), p. 165-170 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/26/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.90-91.165.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of iron doping in La0.8Sr0.2Fe0.05Co0.95O3-δ perovskite (2005)
    Springer
    The European physical journal 43 (2005), S. 297-303 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. La0.8Sr0.257Fe0.05Co0.95O3-δ perovskite is investigated by 57Fe transmission and emission Mössbauer spectroscopy, X-ray diffraction, AC magnetic susceptibility and magnetotransport measurements. Temperature dependence of the 57Fe Mössbauer isomer shift, quadrupole splitting, magnetic hyperfine field, line broadening, and relative spectral area is presented in a detailed manner for La0.8Sr0.257Fe0.05Co0.95O3-δ . The oxidation state of iron is determined to be Fe3+, and the presence of preferential electronic charge compensation Fe3+ ↦  Fe4+ over that of Co3+ ↦ Co4+ is excluded. Relaxation of iron magnetic moments reflected by the 57Fe Mössbauer spectra of La0.8Sr0.257Fe0.05Co0.95O3-δ are interpreted as evidence for the existence of superparamagnetic like Co clusters and a corresponding cluster glass magnetic phase formed below T ≈65 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2005-00057-y
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  • 4
    Electronic Resource
    Electronic Resource
    User-friendly software for Mössbauer spectrum analysis (1996)
    Springer
    Journal of radioanalytical and nuclear chemistry 210 (1996), S. 105-118 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A new user-friendly software for analysis of Mössbauer-spectra has been developed. The program makes use of the advantages provided by the current generation of fast personal computers. An Evolution Algorithm1,2 is used for global search of Mössbauer parameters in order to enhance the reliability of the obtained results. Fitting of Lorentzians, Pseudo-Voigt line profiles, and deriving hyperfine-field distributions including correlations and combinations and Mössbauer Line Sharpening by Fourier transformation provide a wide range of applicability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02055410
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  • 5
    Electronic Resource
    Electronic Resource
    151Eu Mössbauer Study of Calcium Aluminate Glass and Glass Ceramics Containing a Small Amount of Europium(III) (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 57-60 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract 151Eu Mössbauer spectrum of IR-transmitting calcium aluminate glass, 60CaO·32Al2O3·5Fe2O3·3Eu2O3, consists of a broad peak due to distorted Eu(III) with δ and Δ values of 0.91 and −2.02 mm·s−1, respectively. Debye temperatures (θD) of 360 and 320 K were obtained from the temperature dependence of absorption area (A) and that of δ, respectively. These θD values indicate that Eu(III) atoms occupy substitutional sites of distorted Al(III)O4 tetrahedra in calcium aluminate glass. The δ value of 0.62 mm/s obtained from the heat-treated sample (glass ceramic) indicates that Eu(III)-O bonds became less covalent. A smaller Δ value of −1.20 mm·s−1 was obtained for Eu(III) in the glass ceramic, indicating less distorted Eu(III)O4 tetrahedra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006716627539
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  • 6
    Electronic Resource
    Electronic Resource
    Mössbauer Spectroscopy and Preparation of Hg-1223, Tl-1223 and Tl-1212 Superconductors (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 107-112 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Introduction of the Mössbauer nuclei 57Fe into Hg-1223 phase and that of 57Fe and 151Eu into Tl-1212 and Tl-1223 superconductors were investigated. Samples of high phase purity were obtained. Scanning electron microscopy and optical microscopy in normal and polarized light were employed to study the microstructure of the specimens. Energy dispersive X-ray analysis showed that 57Fe in the Hg-based samples and 57Fe as well as 151Eu in the Tl-based compounds, entered superconducting phases. Incorporation of Eu3+ into the superconducting phase favored the formation of the Tl-1212 phase. Mössbauer spectroscopy showed that Eu3+ entered the Ca-site. Two doublets found in the 57Fe Mössbauer spectra in both the Hg-1223 and the Tl-1223 phase referred to two different micro-environments of Fe3+. The assignment of the 57Fe Mössbauer spectra was made under the assumption that Fe favored the 1223 phase. Fe3+ may replace Cu in both the square pyramidal, five-fold oxygen coordinated Cu sites between the Ca and Ba-(Sr)-O layers, and in the square planar, four-fold oxygen coordinated Cu sites the Ca layers in the superconducting phases in both the Hg- and the Tl-based materials. From the relative areas of the two doublets, we concluded that the Fe3+ preferred the square planar Cu site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006797417970
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  • 7
    Electronic Resource
    Electronic Resource
    57Fe Mössbauer Investigation of the Substitutional Effect of Praseodymium in 1-2-3 Compounds (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 117-121 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract 57Fe Mössbauer spectroscopy measurements were performed on the perovskite compounds Eu0.7Pr0.3Ba2(Cu0.99 57Fe0.01)3O7-δ, EuBa1.5Pr0.5(Cu0.99 57Fe0.01)3O7-δ and EuBa1.3Pr0.7(Cu0.99 57Fe0.01)3O7-δ. The observed 57Fe Mössbauer spectra provided an evidence for the correct site assignment of subspectra originating from 57Fe in different microenvironments. Apart from a minor component which was assigned to the 57Fe in the Cu(2) site of the copper oxide plane, all the subspectra could be attributed to the 57Fe in the Cu(1) copper oxide chain site with a fourfold (doublet D1), fivefold (doublet D2) or sixfold (doublet D3) oxygen coordination. In contrast, in the compound EuBa2(Cu0.99 57Fe0.01)3O7-δ the 6-coordinated (D3) species has not been observed. The substitution of Pr for Eu or for Ba resulted in an increased occupancy of the O(5) antichain oxygen sites, which was explained by the charge neutrality criterion. Especially, the replacement of Ba2+ with Pr3+ led to an unusually high degree of occupancy of O(5) sites. In the 57Fe Mössbauer spectra the relative area of the 6-coordinated species (D3) increased, and that of the 4-coordinated one (D1) vanished completely in the case when Pr was substituted for Ba. Furthermore, the proportion of the 6-coordinated (D3) species increased at the expense of the 5-coordinated (D2) one with an increasing concentration of Pr at the Ba site. These experimental results are consistent with the variety of Mössbauer results reported so far.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006753719787
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  • 8
    Electronic Resource
    Electronic Resource
    Mössbauer Spectroscopy and Radiofrequency Absorption Investigations of Pr Substituted 1-2-3 Type Compounds (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 313-316 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract 57Fe and 151Eu Mössbauer spectroscopy as well as RF susceptibility measurements were applied to study the effects of Pr substitution either into the rare earth or into the Ba site in Eu1−x Pr x Ba2Cu3O7−δ and EuBa2−x Pr x Cu3O7−δ, respectively. Site mixing of Pr between the rare earth and Ba sites could be excluded by the utilization of 57Fe Mössbauer spectroscopy. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition independent of the location of Pr. RF susceptibility measurements provide an evidence for a difference in the magnetic moment of Pr substituted for the Eu or Ba sites. The obtained results can be explained by hole filling as the dominant effect of Pr substitution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006770407434
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  • 9
    Electronic Resource
    Electronic Resource
    Structural Investigation of the Effect of Praseodymium in Eu1-xPrxBa2Cu3O7-δ and EuBa2-xPrxCu3O7-δ Perovskites by 151Eu and 141Pr Mössbauer Spectroscopy (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 113-115 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract 151Eu and 141Pr Mössbauer spectroscopy was applied to study the effects of Pr substitution for Eu or Ba atoms in Eu1-x Pr x Ba2Cu3O7-δ and EuBa2-x Pr x Cu3O7-δ, respectively. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition, independent of the location of Pr. This shows that the extra electrons provided by the Pr increase the electronic density in the copper oxide planes and in the 4f orbitals of Eu31, simultaneously. The polycrystalline compound EuBa1.3Pr0.7Cu3O7-δ has been investigated by 141Pr Mössbauer spectroscopy. The observed 141Pr isomer shift, δ(4.2 K) = 0.10(15) mm/s relative to PrF3, reflects a valence state of 3+ for the Pr located at the Ba site in EuBa1.3Pr0.7Cu3O7-δ, being in contrast to the valence state of 3.4+ found earlier for Pr which was situated at the rare earth site. This means that the valence state of Pr substituted for Eu is different from that of Pr substituted for Ba. These results suggest that the suppression of superconductivity by Pr substituted for the rare earth atoms is a consequence of the hole filling effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006749518878
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  • 10
    Electronic Resource
    Electronic Resource
    151Eu and57Fe Mössbauer and X-ray diffraction study of high temperature Tl-containing superconductor (1995)
    Springer
    Journal of radioanalytical and nuclear chemistry 190 (1995), S. 401-405 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract 57Fe and151Eu Mössbauer spectroscopy and X-ray diffractometry measurements were performed with europium and iron containing Tl2(Ca0.8Eu0.2)Ba2(Cu0.98Fe0.02)2O8 and EuBa2Cu3O7-d high temperature superconductor samples in order to study the effect of europium incorporated in a Tl-containing high temperature superconductor. Significant differences have been found between the57Fe Mössbauer spectra of Tl-containing samples with and without Eu or between the151Eu Mössbauer spectra of Tl-containing and 1-2-3 type superconductors. The results can be interpreted by assuming that Eu can be localized at the Ca site in the Tl-containing superconductor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02040018
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