Structure and Magnetic Property Correlation in Nanocrystalline SmFe9

ABSTRACTSmxFe100−x samples with x = 7.6, 10.5 and 12.5 were prepared by high energy ball-milling and subsequent annealing at various temperature Ta, 600 < Ta < 1200 °C. Rietveld analysis coupled to Curie temperature measurements and M6ssbauer spectroscopy revealed for 600 < Ta < 900 °C an hexagonal phase P6/mmm derived from TbCu7 with stoichiometry SmFe9. At Ta > 900 °C, the ordered R3m Sm2Fe17 structure is obtained so that SmFe9 appears as the out-of-equilibrium precursor of Sm2Fe17. The Curie temperature and hyperfine field augmentation found for SmFe9 results from an increase of the interatomic distance in the Fe-Fe dumbbell, responsible for a reduction of the negative exchange interaction.

Distribution of Fe in the fine fractions of some Czech bentonites

Distribution of Fe in the fine fractions of four Czech bentonites was investigated by M6ssbauer spectroscopy. The spectra at room and liquid nitrogen temperatures revealed that most Fe present in the samples is structurally bound in smectite. Microcrystalline and/or Al-substituted goethite was identified in all fine fractions, comprising 8 to 50% of total Fe. This mineral was partly magnetically ordered in the Rokle sample even at room temperature. Two per cent of total Fe was bound in hematite in the Krásný Dvoreček sample. Only octahedral Fe(III) was found in the Rokle and Stebno samples, while Krásný Dvoreček and Hroznětín contained 9 and 38%, respectively, of the total Fe as octahedral Fe(II) and 14% of total Fe was found as tetrahedral Fe(III) in Krásný Dvoreček.

Compared Nitrogen Implantations of Various Alloyed Steels

ABSTRACTNitrogen implantations in pure iron and various stE-els are investigated using nuclear reaction analysis, Conversion Electron M6ssbauer Spectroscopy and Grazing angle X-ray Diffraction. The present work sums up all the significant results although it does not constitue a systematic study. It describes the influence of the chemical composition and the structure effect of the matrix as well as those of the implantation time. The N-martensite, ε-nitride and ε-carbonitride phases are principally identified. The fraction of iron bound with nitrogen is evaluated in the different steels. The strong influence of the small chromium amounts inside the matrix upon the nitride formation is underlined. A preferential orientation of these phases is shown. SIMS experiments are presented in particular to determine the carbon distribution in the first surface layers.

The Mössbauer spectrum of a ferrian muscovite and its implications in the assignment of sites in dioctahedral micas

SummaryA muscovite that contains iron almost entirely in the ferric form has been studied by M6ssbauer spectroscopy. It is established that Fe3+ ions in the sites with cis hydroxyl groups have similar parameters in both muscovite and biotite. By assuming that Fe2+ ions will also have similar parameters for these sites in both minerals the M6ssbauer results of other workers have been reinterpreted. This new interpretation, which is in complete agreement with the X-ray structural analysis of Radoslovich (1960), indicates that in muscovite the sites with cis hydroxyl groups are filled in preference to those with trans hydroxyls. These sites are occupied primarily by trivalent ions. There is possibly a preference for divalent ions by the unique sites with trans hydroxyl groups, but occupation of these sites appears to occur only when the other sites have been filled.