H.-G. Wagner

Mössbauer study of the amorphous alloy Zr100−xFex☆

The hyperfine field distributions were determined from Mossbauer spectra of Fe91Zr9 taken for 6 K < T < 230 K. As in other alloys with invar behaviour, the distribution consists of a high field peak and a broad low field tail. Measurements in external magnetic fields show the ferromagnetic nature of the spin coupling. No evidence was found of an antiferromagnetic component at low fields. For Zr-rich alloys, the distribution of quadrupole splitting was evaluated from the spectra and compared with that found for metastable crystalline alloys. The differences between the two distributions suggest that important changes occur in the short-range order on crystallization.

Mössbauer spectroscopy of amorphous metglass Fe80B20

Abstract Amorphous metals (Metglass Fe 80 B 20 ) have been studied by Mossbauer spectroscopy. In the analysis the radial distribution function of Bernals liquid-structure model has been correlated with the distribution of magnetic hyperfine spectra.

Magnetoelastic effects in amorphous metals due to surface crystallization and oxidation

Abstract In Mossbauer spectra of amorphous ribbons, variations in the relative line intensities indicate reorientations in the domain structure which have sometimes been interpreted as a sign of a bulk structural change. We present evidence that surface oxidation and crystallization are responsible for the observed anisotropies. These effects could be verified by simultaneous observation of the bulk by means of γ-absorption Mossbauer spectroscopy and of the surface by means of (emission) conversion Mossbauer spectroscopy (CEMS).

Mössbauer investigations of the changes in the magnetic properties of amorphous iron rich Fe-Zr alloys with hydrogenation

Abstract The magnetic properties of amorphous iron rich Fe-Zr alloys and their variations with hydrogenation have been studied by 57 Fe Mossbauer spectroscopy and magnetization measurements. Hydrogenation increases both the Curie temperature and the magnetic moment per iron atom. Conversion Electron Mossbauer Spectroscopy (CEMS) showed drastic differences in the compositions of the surface and the bulk material of these alloys.

A direct determination of the quadrupole splitting in ferromagnetic amorphous metals

Abstract We introduce a new method for direct determination of the quadrupole splitting of amorphous alloys in the ferromagnetic state. The radio frequency induced collapse of the magnetic hyperfine structure leaves pure quadrapole split Mossbauer spectra. This allows the direct evaluation of the distribution of quadrupole splittings and isomer shift.

Mössbauer investigations of ferromagnetic amorphous metals in radio frequency fields

Abstract Exposure to radio frequency (rf) magnetic fields leads to reversible and irreversible changes in Mossbauer spectra of amorphous ferromagnets. We discuss these changes, showing that the irreversible effects reflect rf-induced crystallization caused by magnetostrictive vibrations. From the sideband intensities the displacement of the Mossbauer nuclei along the direction of the γ-rays can be estimated. For materials where the full rf-collapse can be observed it is possible to determine directly the value of the quadrupole splitting in the ferromagnetic state.

Short range order in metallic glasses from quadrupole splitting distributions

Changes are observed in the short range order of several Fe based amorphous alloy systems through the quadrupole splitting distributions. The quadrupole splittings are determined directly in the ferromagnetic state by using the radio frequency collapse of the magnetic splitting.

Crystallization of amorphous metals

An important factor for the application of amorphous metals is their crystallization temperature. This can be enhanced by addition of transition metals in Fe80B20. Other properties e.g. zero magnetostriction, can then be achieved by alloying. In this paper we investigate the crystallization mechanism, the phases produced and the influence of transition metals (T) in Fe80−xTxB20.

Mixed hyperfine interaction in amorphous Fe-Zr sputtered films in external magnetic field — A57Fe Mössbauer study

Conventional57Fe-Mössbauer spectroscopy provides only information about the magnitude of the splitting QS in the case of electric quadrupole hyperfine interaction, but not on the sign of the main component of the electric field gradient (EFG), Vzz, or the asymmetry parameter, η, which are sensitive to the local environment of the57Fe nuclei. This kind of information is obtained by measurements in external magnetic fields. In the case of amorphous Fe-Zr sputtered films mixed hyperfine interaction leads to a clear change in the behaviour of the Zr-rich and the Fe-rich alloys, indicating the existence of magnetic clusters in the Fe-rich samples.

Toroidal proportional detector for backscattered Mössbauer γ-and x-rays

First results with a toroidal proportional detector for Mössbauer spectroscopy of backscattered γ-and X-rays are presented.