0000000000034574
AUTHOR
P. Griesbach
showing 13 related works from this author
Ni61Mössbauer study of the hyperfine magnetic field near the Ni surface
1987
$^{61}\mathrm{Ni}$ M\"ossbauer measurements have been performed at 4.2 K on spherical Ni particles covered with a protective layer of SiO, with average diameter of 500 and 50 \AA{}. The hyperfine magnetic field at $^{61}\mathrm{Ni}$ nuclei for 500-\AA{} particles has been found to be 78.3(4) kOe, compared with the field for Ni foil of 75.0(2) kOe. The small difference is due to the demagnetization and dipolar fields in 500-\AA{} particles. The spectrum of 50-\AA{} particles has a surface component with the corresponding value of the hyperfine magnetic field of 40.3(5.4) kOe. This strongly indicates that, in accordance with recent theoretical studies, there is a decrease of the hyperfine mag…
Problems of electron detection in Depth-Selective Conversion Electron Mössbauer Spectroscopy
1992
Applications of Depth-Selective Conversion Electron Mossbauer Spectroscopy (DCEMS) are limited by the long measuring times needed for collecting sufficient data statistics. To shorten the recording time, the background should be reduced and the detection efficiency for conversion electrons should be improved. For57Co/57Fe DCEMS, systematic studies were performed to investigate the origin, shape, and structure of the background components in DCEMS data distributions for various samples using channeltrons and low-noise scintillation counters as electron detectors.
57Fe,61Ni, and121Sb M�ssbauer study of oxidic spinel ferrites CoxNi5/3?xFeSb1/3O4
1987
Antimony substituted nickel ferrites Co x Ni5/3−xFeSb1/3O4 withx=0,1/3,1,4/3, and 5/3 were prepared by the common ceramic technique, and the single-phase structure was confirmed by x-ray powder diffraction.57Fe Mossbauer spectra were recorded at 4.2 K with and without an applied magnetic fieldHlong=60 kOe in order to determine the cation distribution and the spin structure. Utilizing the cation distributions and the Yafet-Kittel spin structures for B-site Fe3+ ions, derived from Mossbauer experiments the calculated magnetic moments are in excellent agreement with the experimental values at 4.2 K. The existence of Ni2+ ions in crystallographic A-sites was confirmed by61Ni Mossbauer spectrosc…
The state of iron in andalusite
1990
Iron in andalusite (Al2SiO5) with concentrations of 1.5 … 4.3 wt-% has been reported in the literature to occupy mainly Al1 sites as Fe3+, and only small portions occupy Al2 sites as Fe3+ and Fe2+. In no case a magnetic hyperfine splitting has been found at temperatures above 77 K.
61Ni Mössbauer study of the surface hyperfine magnetic field in nickel
1988
61Ni Mossbauer measurements have been performed at 4.2 K on spherical Ni particles with an average diameter of 100 and 30 A, covered with a protective layer of SiO. Their spectra contain a surface component with a significantly reduced hyperfine magnetic field as compared with the field in the bulk. This result confirms recent theoretical predictions.
Low noise scintillation detectors with a P-47 thin layer screen for electrons of several keV
1994
Abstract The applicability of a low-noise scintillation detector (ScD) for the registration of electrons of several keV energy has been studied employing photomultipliers (PM) of different types and sizes. With the application of a sedimented P-47 scintillation screen, the values of the low-energy sensitivity limit and those of the light conversion coefficient were determined as about 2.7–4.7 keV and 2.8–6.6 photoelectrons/keV, respectively, for the set of PM's (Philips-Valvo XP 2020, Philips-Valvo XP 2052, Philips-Valvo XP 2972, EMI 9124a) studied. It is concluded that such scintillation detectors might be used advantageously as electron counters in the range of E > 5 keV. Applications bel…
Ni participation in the magnetism of Fe-Ni-Si-B amorphous alloys.
1987
$^{61}\mathrm{Ni}$ M\"ossbauer measurements at 4.2 K have been performed on (${\mathrm{Fe}}_{\mathrm{x}}$${\mathrm{Ni}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${)}_{77}$${\mathrm{Si}}_{1013}$ amorphous alloys with x=0.0, 0.1, and 0.9. Ni atoms in ${\mathrm{Ni}}_{77}$${\mathrm{Si}}_{10}$${\mathrm{B}}_{13}$ bear no magnetic moment, whereas in (${\mathrm{Fe}}_{0.1}$${\mathrm{Ni}}_{0.9}$${)}_{77}$${\mathrm{Si}}_{10}$${\mathrm{B}}_{13}$ and (${\mathrm{Fe}}_{0.9}$${\mathrm{Ni}}_{0.1}$${)}_{77}$${\mathrm{Si}}_{10}$${\mathrm{B}}_{13}$ their moments are, respectively 0.38${\ensuremath{\mu}}_{B}$ and 0.65${\ensuremath{\mu}}_{B}$. Our results, together with the literature data, show that Ni atoms in Fe-…
Optimization of a conversion electron Mössbauer spectroscopy gas flow He/CH4 proportional counter
1992
A new detector for CEMS has been built and optimized with respect to the statistical quality of spectra obtained. The optimization has been performed by measuring Mosbauer and pulse height spectra at in- and off-resonance. Single channel analyzer settings were calculated by a new optimization routine. A comparison of different detector designs has been performed using the statistical utility rate of spectra obtained from a stainless steel foil. A procedure for determining optimal operating parameters for ICEMS gas flow proportional counters is proposed.
AES and CEMS analysis of the formation of layers on Si steel under thermal treatment in a flux of H2/water vapour
1991
The near surface diffusion and reaction processes in iron-silicon steel (3.1 wt.%Si) during 10 min decarburization in water vapour/hydrogen have been studied. The decarburization temperature has been varied between 506 and 714°C for the fixed partial pressure ratio pH2O/pH2=0.017. An outer layer of SiO2 forms on the surface with its thickness increasing with temperature. From 600°C upwards, the decarburization process is hindered and a cementite layer is formed below the SiO2 layer. The formation of fayalite at the surface has been studied at a fixed decarburization temperature with pH2O/pH2 ranging from 0.017 to 0.49. The scale thickness reduces abruptly just before the ratio pH2O/pH2 nece…
Quantitative determination of fayalite layers on iron by CEMS
1990
In the processing of silicon iron (Fe-3%) Si), so-called ‘fayalite layers’ are formed. By CEMS, they were found to consist of an outer Fe3+-oxide layer and an inner Fe2SiO4 (fayalite) layer. Sometimes an additional wustite contribution was found. Thef-factor of fayalite was determined experimentally (ffayalite/fα-Fe=0.47±0.04) and, by use of it, the thicknesses of the layers on some silicon iron samples could be calculated from CEMS data.
Layer formation on silicon steel by processing in H2/H2O at elevated temperatures
1992
Silicon steel (Fe-3wt%Si), as used for transformers and generators, has been annealed in wet hydrogen at elevated temperatures. The composition, sequence, and thicknesses of the layers found by conversion electron Mossbauer spectroscopy (CEMS) and Auger electron spectroscopy (AES) depth profiling for a 10 minutes anneal in different atmospheres are reported. In the range from 500°C to 720°C we observed carbide formation, indicating that the decarburization is hindered. Above 800°C, the layers consist of fayalite or of fayalite and iron oxides, depending on the oxygen potentialaO. At 843°C, the onset of iron oxide formation was found ataO=0.33.
Technical Note:Study of the Cl−-Induced Breakdown of the Passive Layer on Steel
1991
Abstract The Cl−-induced breakdown of the passive layer on a standard steel has an induction time that increases in a nearly linear fashion with the previous holding time (at the passivation potent...
The effect of energy-dependent detector efficiency in electron spectroscopic methods: XPS, AES and DCEMS
1993
Systematic studies were performed to investigate the distorting effect of the electron energy dependence of the channeltron detector efficiency on the shape of data distributions in electron spectroscopy. In agreement with earlier results for electron energies up to 3 keV, it was found that a virtually energy-independent shape of the electron distribution might be achieved even in a very broad range of electgron energies (up to 15 keV) by appropriate selection of the operational high voltage of a channeltron. However, the efficieny of channeltrons was also found to depend on count rates, indicating one of the principal difficulties in comparing distribution recorded under different experime…