E. Kuzmann

User-friendly software for Mössbauer spectrum analysis

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.

Critical review of analytical applications of Mössbauer spectroscopy illustrated by mineralogical and geological examples (IUPAC Technical Report)

We have developed a new terminology for Mössbauer pattern analysis in order to enhance the performance of qualitative analysis by Mössbauer spectroscopy. In this approach, Mössbauer parameters are considered as a function of a number of externally adjusted experimental parameters at which the spectrum has been recorded. The basis of analytical classification is the microenvironment, which is determined by an assembly of atoms causing the same hyperfine interactions at one particular class of the Mössbauer probe atoms.Since Mössbauer spectroscopy measures hyperfine interactions very sensitively, the microenvironment presents itself as a fundamental concept for analytical purposes. Our approach can also help to systematize the Mössbauer data for the identification of individual physicochemical species from the corresponding patterns present in the spectrum.

Metastability in EuBa2(Cu1-xSnx)3O7-y studied by 119Sn and 151Eu Mössbauer spectroscopy.

The metallic oxide compound system EuBa/sub 2/(Cu/sub 1-//sub x/Sn/sub x/)/sub 3/O/sub 7-y/ (x = 0.05, 0.10, 0.20) was prepared for investigation with /sup 151/Eu and /sup 119/Sn Moessbauer spectroscopy. The best fits of the /sup 119/Sn Moessbauer lines reveal at least two different Sn/sup IV/ sites. The /sup 151/Eu spectra are characteristic for Eu/sup III/ state in these compounds. We have found a considerable difference between the shapes of /sup 119/Sn Moessbauer spectra recorded at room temperature and those recorded at the temperature of liquid nitrogen in the case of the sample having the highest tin content. Nevertheless, there is no evidence that this difference has a direct connection with the superconducting behavior.

A comparative study of Mössbauer spectroscopy and X-ray diffraction for the elucidation of the microstructure of electrodeposited FeCrNi alloys

Mossbauer spectroscopy and X-ray diffractometry have been used to study electrodeposited Fe1−x−yCrxNiy (10 ⩽ x ⩽ 24, 25 ⩽ y ⩽ 36) alloys. The main phase of the as-deposited samples was found to be microcrystalline having f.c.c. structure. The f.c.c. phase of the electroformed samples was ferromagnetic, contrary to the thermally prepared alloys of the same composition, which were paramagnetic. The electrochemically prepared materials also contain some microcrystalline paramagnetic phases. The hyperfine field distribution analysis of the Mossbauer spectra shows, that a precipitation process takes place in the electrodeposits, due to the heat treatment.

57Fe Mössbauer spectroscopy and electron paramagnetic resonance studies of human liver ferritin, Ferrum Lek and Maltofer®

A human liver ferritin, commercial Ferrum Lek and Maltofer® samples were studied using Mössbauer spectroscopy and electron paramagnetic resonance. Two Mössbauer spectrometers have been used: (i) a high velocity resolution (4096 channels) at 90 and 295K, (ii) and a low velocity resolution (250 channels) at 20 and 40 K. It is shown that the three studied materials have different superparamagnetic features at various temperatures. This may be caused by different magnetic anisotropy energy barriers, sizes (volume), structures and compositions of the iron cores. The electron paramagnetic resonance spectra of the ferritin, Ferrum Lek and Maltofer® were decomposed into multiple spectral components demonstrating the presence of minor ferro- or ferrimagnetic phases along with revealing marked differences among the studied substances. Mössbauer spectroscopy provides evidences on several components in the measured spectra which could be related to different regions, layers, nanocrystallites, etc. in the iron cores that coincides with heterogeneous and multiphase models for the ferritin iron cores.

Local environments of iron and cobalt in doped MgB2 superconductors

MgB2 has been doped with 57Fe and 57Co in order to probe the electronic structure of the superconductor by Mossbauer spectroscopy. Simultaneous SEM–EDX studies showed that both Fe and Co were incorporated to some extent into the MgB2 host lattice. Mossbauer spectroscopy indicated that Fe2B and FeB were also formed during the preparation. At higher Fe contents Fe2B appeared unambiguously as a secondary phase in the x-ray diffraction. CoB was detected at substitution levels of 10 mol% and greater. Both Fe and Co doping decreased the Tc(0) modestly. Co and Fe were found to substitute at the Mg site in the MgB2 lattice. The Mossbauer parameters for 57Co and 57Fe were consistent with a metallic environment. The similarity of the isomer shifts in MgB2 and in cuprate superconductors is being discussed.

Exchange of iron ions into layers of α-zirconium phosphate

Abstract Exchange of Fe 3+ and Fe 2+ ions into layers of α-zirconium phosphate is achieved in aqueous media by using monosodium and/or ethanolic forms of the host precursor. The products obtained are characterized by chemical analysis, X-ray powder diffraction and Mossbauer spectroscopy. For site assignments, structural modeling is used by combining the measured and simulated X-ray diffractograms. Fe 3+ ions are incorporated only in part, and a biphasic product is obtained. Exchange of Fe 2+ ions leads to a single phase with 50% iron loading with Fe 2+ ions located in two different coordination states. On a long-term storage in open air, Fe 2+ →Fe 3+ oxidation proceeds without noticeable change in the crystal structure.

Mössbauer and X-ray study of rapidly quenched and mechanically alloyed Al-Fe alloys

Mössbauer spectroscopy and X-ray diffractometry were used to study the effect of the cooling rate as well as of the milling time on the structure of rapidly quenched Al-6.8% Fe, Al-0.5% Fe and mechanically alloyed Al-8% Fe alloys. The main phase of the rapidly quenched alloys was identified as AlmFe besides Al6Fe andAlFe solid solutions. In the mechanically alloyed samples (with milling time between 1.5–43 hours), we have found α-Fe, AlFe solid solution and a third phase characterized by a doublet with Mössbauer parameters which are not so far from those of clusters inAlFe alloys. We have observed a continuous increase of the quantity ofAlFe solid solution, together with a significantly less increase of the third phase as a function of the milling time. Simultaneously, the quantity of alpha-iron has gradually decreased.

Metastability in EuBa/sub 2/(Cu/sub 1-//sub x/Sn/sub x/)/sub 3/O/sub 7-y/ studied by /sup 119/Sn and /sup 151/Eu Moessbauer spectroscopy

The metallic oxide compound system EuBa/sub 2/(Cu/sub 1-//sub x/Sn/sub x/)/sub 3/O/sub 7-y/ (x = 0.05, 0.10, 0.20) was prepared for investigation with /sup 151/Eu and /sup 119/Sn Moessbauer spectroscopy. The best fits of the /sup 119/Sn Moessbauer lines reveal at least two different Sn/sup IV/ sites. The /sup 151/Eu spectra are characteristic for Eu/sup III/ state in these compounds. We have found a considerable difference between the shapes of /sup 119/Sn Moessbauer spectra recorded at room temperature and those recorded at the temperature of liquid nitrogen in the case of the sample having the highest tin content. Nevertheless, there is no evidence that this difference has a direct connection with the superconducting behavior.

Mössbauer study of electrodeposited Fe−Cr−Ni alloys

Mössbauer spectroscopy was used to compare Fe−Cr−Ni alloys prepared by different electrochemical as well as thermal methods. The main phase of the electrodeposits was ferromagnetic contrary to the thermally prepared alloys of same composition, which were paramagnetic. Obvious differences can be observed among the spectra of electrodeposited samples of different composition. Narrower line width and smaller paramagnetic contribution can be observed in samples electrodeposited onto A1 substrate compared to those in samples plated onto graphite with modified electrochemical parameters. Changes in hyperfine field distribution of as-deposited and aged samples indicate a precipitation process due to the heat treatment.