共查询到20条相似文献,搜索用时 975 毫秒
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《Journal of magnetism and magnetic materials》2003,262(1):56-59
Magnetic and magnetotransport measurements were performed on gas-phase synthesized Fe nanoparticles subjected to surface oxidation and cold consolidation. Two samples were investigated with α-Fe volume fraction of 0.15 and 0.60. The sample with smaller metallic fraction is below the percolation threshold for metallic conduction and the conduction mechanism is dominated by thermally activated processes across the oxide. In this case, by lowering the temperature, an increase of the negative magnetoresistance is observed up to 5% at 50 K in a magnetic field of 70 kOe. The magnetoresistance dependence on the sample magnetization, temperature and sample composition is discussed considering the magnetic correlations present in these nanostrucuterd systems. 相似文献
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Here, we report experimental results on melting and subsolidus phase relations in the Fe–Fe2P system at 6?GPa and 900–1600°C. The system has two P-bearing compounds: Fe3P and Fe2P. X-ray diffraction patterns of these compounds correspond to schreibersite and barringerite, respectively. The Fe–Fe3P eutectic appears at 1075°C and 16?mol% P. Schreibersite (Fe3P) melts incongruently at 1250°C to produce barringerite (Fe2P) and liquid containing 23?mol% P. Barringerite (Fe2P) melts congruently at 1575°C. Maximum solid solution of P in metallic iron at 6?GPa is 5?mol%. As temperature increases to 1600°C, the P solubility in the metallic iron decreases to 0.5?mol%, whereas the P content in coexisting liquid decreases to 3?mol%. The composition of quenched phases from Fe–P melt coincides with the compositions of equilibrium phases at corresponding temperature. Consequently, the composition of quenched products of Fe-P melts in meteorites can be used for reconstruction of P–T conditions of their crystallization under ambient or low pressures or during shock melting by impact collisions. 相似文献
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H. R. Rechenberg 《Hyperfine Interactions》1990,54(1-4):683-687
Mössbauer spectra of Fe1?x Ni x withx=0.40, 0.35 and 0.32 were taken at various temperatures and fitted withB hf distributions. TheP(B hf) curves generally show a peak and a low-field tail. The peakB * and the average \(\bar B\) were obtained in theT→0 limit. Fe moments were deduced from these data with help of a semiempirical equation. While the average \(\bar \mu _{Fe} \) decreases withx (invar anomaly), a large fraction of Fe atoms retain the strong moment (≈ 2.7 μB) typical of Ni-rich alloys. This result is consistent with a two-states model for invar. 相似文献
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Technical Physics - Magnetized and unmagnetized Co–Fe and Ni–Fe alloys fabricated on a two-high casting installation in the form of thin flexible amorphous films are promising materials... 相似文献
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Magnetic properties of multilayered Fe/Dy films with artificial superstructures have been investigated by57Fe Mössbauer spectroscopy. Doublet peaks are observed at room temperature when the Fe layer is thinner than 20Å. Mössbauer spectra for thicker Fe layers correspond to α-Fe spectra. In certain samples, i.e. [Fe(44Å)/Dy(6Å)], a gradual spin reorientation takes place, which is evidenced from the change of relative intensities of Δm=0 lines with decreasing temperature. 相似文献
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Fe含量和粒径对Fe/Cu颗粒膜结构和磁性的影响 总被引:4,自引:1,他引:3
采用共蒸发法制备不同组分的Fe/Cu颗粒膜,将样品分两组进行退火和不退火处理. 根据测量及分析,确定了不同成分的Fe/Cu颗粒膜的相组成和晶体结构;找出了 Fe/Cu颗粒膜矫顽力与粒径的关系,利用此关系由自发形核理论可知,提高功率,快速蒸镀薄膜,可得到细密颗粒的Fe/Cu颗粒膜,从而降低矫顽力,减少磁滞损耗. 相似文献
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V. S. Rusakov K. K. Kadyrzhanov A. L. Kozlovskiy T. Yu. Kiseleva M. V. Zdorovets M. S. Fadeev E. N. Luk’yanova 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(7):831-835
Iron and iron–cobalt nanostructures are probed by means of Mössbauer spectroscopy combined with scanning electron microscopy, energy-dispersion analysis, and X-ray diffraction. The obtained nanostructures are single-phase Fe1 ? xCo x (0 ≤ x ≤ 1) nanotubes that have high degrees of polycrystallinity and a bcc lattice 12 μm long and 110 ± 3 nm in diameter, with walls 21 ± 2 nm thick. A random distribution of the orientations of the magnetic momenta of Fe atoms are observed for Fe nanotubes, while Fe–Co nanotubes are characterized by a magnetic texture along their axes. 相似文献
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Structure and magnetic properties of nanocrystalline P6/mmm out-of-equilibrium precursors of hard magnetic R-3m Sm2(Fe,M)17C (M=Ga,Si,) and I4/mmm Sm(Fe,Co,Ti)11 equilibrium phases, are presented. Their structure is explained with a model ground on the R1???s T5?+?2s formula (R=rare-earth, s=vacancy rate, T=transition metal) where s Sm atoms are statistically substituted by s transition metal pairs. The Rietveld analysis (RA) provides the stoichiometry of the precursors, 1:9 and 1:10, respectively precursor of 2:17 and 1:12 phases. The interpretation of the Mössbauer spectra of the 1:9 and 1:10 phases, is based on the correlation between δ and the Wigner–Seitz Cell volumes, calculated from the structural parameters. The δ behaviour of each crystallographic site versus Co content, defines the Co location while it confirms that of Si and Ga obtained by RA. Substitution occurs in 3 g site, whatever Co or M. The Sm(Fe,Co,Ti)10 and Sm(Fe,M)9C Curie temperature (Tc) are compared to those of the equilibrium phases, the effects of Fe substitution and C addition are discussed. The maximum μ 0Hc is obtained for low M or Co content, for auto-coherent diffraction domain size ~30 nm. SmFe8.75Ga0.25C and SmFe8.75Si0.25C with Tc of 680 and 690 K, show respectively Mr and μ 0Hc of 58 emu/g, 27 kOe and 95 emu/g, 15 kOe, values higher than those obtained for Sm2(Fe,M)17 carbides. 相似文献
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采用第一性原理研究了H2O分子在Fe(100),Fe(110),Fe(111)三个高对称晶面上的表面吸附.结果表明,H2O分子在三个晶面上的最稳定结构皆为平行于基底表面的顶位吸附结构.H2O分子与三个晶面相互作用的吸附能及几何结构计算结果表明H2O分子与三个晶面的相互作用程度不同,H2O分子与Fe(111)晶面的相互作用最强,其次是Fe(100),相互作用最弱的是Fe(110)表面,而这与晶面原子的排列密度相关.吸附体系的电子结构计算结果也得出了相似的结论.同时电荷布居分析表明,H2O分子与Fe表面相互作用时,O原子与基底原子之间的电荷交换使基底Fe原子表面带负电,导致表面电位降低,也促使Fe表面更易于发生电化学腐蚀反应. 相似文献
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With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. To this end, the iron-based superconductor Lu2Fe3Si5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (Tc=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. The value of Debye temperature was estimated from temperature dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near Tc, nor phonon softening were observed. 相似文献
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采用X射线衍射技术研究了A1-Fe-Ce合金的非晶结构,发现非晶态合金X射线强度曲线上都丰在明显的预峰,合金随铁含量增加,预峰和主峰向大角度偏移;合金随铈含量增加,预峰和主峰向小解度偏移。250℃时,非晶合金出现铝相晶化,而预峰的形状和位置并未发生改革;400℃时央预峰消失的位置形成多种化合物相。Fe原子大部分存在于预峰所对应的A1-Fe-Ce原子团簇中,崦Ce原子大部分无规分布于A1非晶基体中。 相似文献
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Juliana C. Trist?o José D. Ardisson Maria Terezinha C. Sansiviero Rochel M. Lago 《Hyperfine Interactions》2010,195(1-3):15-19
The production of magnetic nanoparticles of Fe3O4 or Fe0 coated with carbon and carbon nanotubes was investigated by the reduction of hematite with ethanol in a Temperature Programmed Reaction up to 950°C. XRD and Mössbauer measurements showed after reaction at 350°C the partial reduction of hematite to magnetite. At 600°C the hematite is completely reduced to magnetite (59%), wüstite (39%) and metallic iron (7%). At higher temperatures, carbide and metallic iron are the only phases present. TG weight losses suggested the formation of 3–56 wt.% carbon deposits after reaction with ethanol. It was observed by SEM images a high concentration of nanometric carbon filaments on the material surface. BET analyses showed a slight increase in the surface area after reaction. These materials have potential application as catalyst support and removal of spilled oil contaminants. 相似文献
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《Journal of magnetism and magnetic materials》2001,224(1):65-75
A RHEED study shows quasi layer-by-layer growth in BCC Fe/Cu/Fe(0 0 1) structures. The BCC stacking of Cu layers is maintained up to a critical thickness of 11 layers. The different iron sites at the Fe/Cu interfaces can be identified by Mössbauer spectroscopy from the distinct values measured for the magnetic hyperfine fields Hhf and isomer shifts at the 57Fe nuclei. This makes it possible to determine the concentration of 57Fe atoms in the different iron sites. The roughness of the Cu on Fe interface estimated from the Mössbauer study is more pronounced than that estimated from a RHEED study of the structure. The growth of Fe on Cu produces CuFe alloy layers at the Cu/Fe interface. 相似文献
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