Search results for "SB"
showing 10 items of 1841 documents
57Fe and119Sn Mössbauer investigations on some substituted barium hexaferrites
1994
57Fe and119Sn Mossbauer measurements have been carried out on powder samples of three differently substituted M-type barium hexaferrites. By57Fe Mossbauer measurements in an external magnetic field applied parallel to the γ-ray direction, we found a canted spin structure for all samples. Furthermore, we detected a strong preference of the Sn4+ ions for the 4f2 sites. From57Fe Mossbauer measurements aboveT N, we conclude that the substitution does not influence the 2b sites. The analysis of the magnetically split119Sn Mossbauer spectra at room temperature in the case of the Co-Sn and Zn-Sn substituted samples shows a strong difference between the two. The spectra were interpreted due to the …
Lamb-Mössbauer factor in the spin crossover compound Fe(tpa)(NCS)2
1994
The Lamb-Mossbauer factor in spin crossover compounds has been the subject of controversial discussions in the literature. For several compounds, a significantly larger Lamb-Mossbauer factor for the complex molecules in the low-spin (fls) than in the high-spin (fhs) state has been reported, while for compounds studied in our laboratory such differences could not be observed. We prepared the compound Fe(tpa)(NCS)2, thef factors of which were reported to be very different. We could not prove thef factors of this compound to be different. The implications of a different structural phase of compound prepared by us are discussed.
A Portable Readout System for Microstrip Silicon Sensors (ALIBAVA)
2009
A readout system for microstrip silicon sensors has been developed. This system is able to measure the collected charge in one or two microstrip silicon sensors by reading out all the channels of the sensor(s), up to 256. The system can operate either with non-irradiated and irradiated sensors as well as with n-type and p-type microstrip silicon sensors. Heavily irradiated sensors will be used at the Super Large Hadron Collider, so this system can be used to research the performance of microstrip silicon sensors in conditions as similar as possible to the Super Large Hadron Collider operating conditions. The system has two main parts: a hardware part and a software part. The hardware part a…
High-performance Mössbauer spectroscopy: Criteria, possibilities, limitations
1992
Increasing attention is being paid to non-conventional Mossbauer methods in view of the extension of Mossbauer Spectroscopy (MS) to a broadening field of applications. With such long-lasting experiments the shortening of the measuring time required for a given statistical significance is of major practical importance. It is shown that the statistical utility rateu allows one to determine which experimental parameters have a primary role, and it also enables sucessive optimization. It is pointed out for various MS measurements that the strategy for improving the experimental performance is strongly dependent on the given problem. As examples, time-differential Mossbauer measurements and conv…
Mössbauer Study of Lanthanum–Strontium Ferromanganite Oxides
2004
The La0.88Sr0.2Mn(1−y)Fey0(3±δ, i (LSMF with y = 0, 0.2, 0.5, 0.8, 1) compounds are prospective cathode materials for advanced solid oxide fuel cells (SOFC) application operating at 700° C. Usual analysis methods like thermogravimetric analysis or redox titration enable to determine the average oxidation state of both manganese and iron cations. The comparative role of iron and manganese in B-site was evaluated by 57Fe Mossbauer spectroscopy. Spectra revealed that the complete substitution of iron for manganese induces the formation of Fe5+ for the compound with y = 1. However, no tetravalent iron cation was observed in air for the LSMF compounds with y = 0.2, 0.5 and 0.8. This means that o…
Study of Fe−Ti and Fe−TiN interfaces by conversion electron Mössbauer spectroscopy
1992
Titanium and titanium nitride-iron interfaces obtained by PVD coated thin films of Ti and TiN onto argon plasma etched iron substrates at various temperatures and negative bias were studied by use of CEMS. It was found that intermixing to Ti with Fe resulted in the appearance of an amorphous FeTi1−x phase. Furthermore, a comparison of CEM spectra of samples before and after heating in UHV has shown rather strong influence of thermal treatments on Fe/Ti as well as Fe/TiN interfaces.
Observation of substitutional Fe in CEMS measurements on synthetic CVD diamond
2004
Conversion electron Mossbauer spectroscopy measurements have been made on a diamond sample synthesized by chemical vapour deposition. The sample was implanted with 70 keV 57Fe to a dose of 5 × 1014 cm−2 and Mossbauer measurements were made on the as-implanted sample and after annealing at temperatures of 600 K, 950 K and 1470 K. The spectra at the lower temperatures were characterized by broad doublets, but the annealing at 1470 K resulted in dramatic decrease in the intensity of the doublet components, and the appearance of a strong single line with an isomer shift of δ = −0.90(5) mm/s and areal intensity of 30%, and a weaker line (5%) with δ = +0.07(4). Arguments are presented to attribut…
Recent developments in the evaluation of Mössbauer line intensities
1985
The angular dependence of the intensities of pure or mixed multipole transitions is formulated in a new fashion, which takes into account arbitrary texture of the Mossbauer absorber ranging from complete orientation (single crystals) over preferred orientation to random powders and an anisotropic absorption fraction of the nuclei. The application of the theory is demonstrated by means of typical examples from the literature.
Electric hyperfine interaction in199Hg fluorides
1985
With the current integration technique, the Mossbauer effect on the 158 keV, 5/2−→1/2− transition in199Hg was studied using the cubic HgF2 and the tetragonal Hg2F2 as absorbers; in the latter, a quadrupole splittingeQVzz=}- 9.0(2) mm/s was observed. Electron densities were calculated with the self-consistent-charge-extended-Hueckel-molecular-orbital method and δ〈r2〉=(3.26±0.11) fm2 derived. From the quadrupole splitting and the calculation, an effective antishielding factor almost twice that of the neutral Hg atom is derived.
Mössbauer effect study of the temperature and pressure dependence of the singlet-quintet intersystem crossing dynamics in an iron(II) spin crossover …
1988
The lineshapes of Mossbauer spectra of the iron(II) spin crossover complex [Fe(6-mepy)3 tren] (PF6)2 are affected by the dynamics of the HS⇌LS equilibrium. The lineshapes are reproduced with a stochastic two-state-relaxation-model yielding rate constants similar to those determined for related complexes in solution. Application of an external pressure of 150 MPa increases the relaxation rate.