Ph. Bauer

Ion Beam Mixing Effects Induced in the Latent Tracks of Swift Heavy Ions in a Fe/Si Multilayer

By following the experimental results recently published about electronic-energy-deposition-induced effects in metallic materials, a mixing effect is observed in an Fe/Si multilayer irradiated by 650 MeV uranium ions. Mossbauer spectroscopy shows that, after a fluence as low as 1013 cm-2, an Fe 4.5 nm/Si 3.5 nm multilayer has been made almost homogeneous by ion mixing. On electron micrographs, at very low fluence, latent tracks are observed where the magnetic properties are drastically modified from the previous crystalline ferromagnetic state.

Magnetic and structural properties of iron nitride thin films obtained by argon‐nitrogen reactive radio‐frequency sputtering

We have prepared iron nitride thin films by reactive rf sputtering of an iron target in an argon‐nitrogen plasma. The films present a wide variety of structures and compositions: α expanded bcc iron, amorphous Fe1−x‐Nx, γ’‐Fe4N, e‐Fe2–3N, and ζ‐Fe2N. Evolutions of the crystallographic structures and of the magnetic properties of the obtained phases are discussed versus the nitrogen concentration in the gaseous flow and the substrate temperature during deposition.

High electronic excitations and ion beam mixing effects in high energy ion irradiated Fe/Si multilayers

Mossbauer spectroscopy (57Fe) shows evidence for mixing effects induced by electronic energy deposition in nanoscale Fe/Si multilayers irradiated with swift heavy ions. A decrease in the mixing efficiency with electronic stopping power is reported; a threshold is found, under which iron environment modifications no longer occur. The kinetics of Fe–Si phase formation after irradiation suggests the existence of three regimes: (i) for high excitation levels, a magnetic amorphous phase is formed directly in the wake of the incoming ion and an almost complete mixing is reached at low fluence (1013 U/cm2); (ii) for low excitation levels, a paramagnetic Si-rich amorphous phase is favored at the interface while crystalline iron subsists at high fluences; (iii) for intermediate excitation levels, saturation effects are observed and the formation rate of both magnetic and paramagnetic phases points to direct mixing in the ion wake but with a reduced track length in comparison to U irradiation. The measured interfac...

Mössbauer study of the kinetics of simulated corrosion process of iron in chlorinated aqueous solution around room temperature: The hyperfine structure of ferrous hydroxides and Green Rust I

The hyperfine structure of the two ferrous hydroxides, Fe(OH)2, [2Fe(OH)2, FeOCl] and Green Rust I obtained during the oxidation of iron in chlorinated aqueous medium is determined. The structure of GRI is proposed. The kinetics of oxidation and the role of the chlorine concentration is thoroughly discussed.

Cems study of the carbon distribution in austenite

CEMS resolution allows a careful study of Fe−C pure austenite spectra with high carbon content. Three Fe environments are detected which are ascribed to Fe atoms with one carbon first nearest neighbour and zero carbon second nearest neighbour and two environments with no carbon first nearest neighbour but zero carbon second nearest neighbour and one to four carbon second nearest neighbours respectively. This confirms the repulsive interaction between carbon interstitials and the tendency towards Fe8C ordering is suggested.

Hyperfine interactions and structures of ferrous hydroxide and green rust II in sulfated aqueous media

A sulfated ferrous hydroxide is obtained by mixing NaOH with melanterite depending on the R=[SO4−−]/[OH−] ratio and leading by oxidation to the green rust II transient compound. Hyperfine parameters are presented.

GROWTH AND CHARACTERIZATION STUDIES OF FE4N THIN FILMS PREPARED BY ION BEAM ASSISTED EVAPORATION

Thin films of iron nitrides have been prepared using an ion beam assisted evaporation method. X‐ray diffraction and Mossbauer spectrometry show that the films generally consist in a mixture of Fe and Fe4N phases. For high source powers and temperatures higher than 300 °C it was possible to obtain the pure Fe4N phase.

57Fe Mössbauer spectroscopy from Tb/Fe and Er/Fe multilayers

Mossbauer spectroscopy was carried out on Tb/Fe and Er/Fe multilayers. The dependence of the extension of the interface on the substrate temperature during the deposition process and its magnetic behaviour are shown. Easy plane of magnetization and perpendicular easy axis of magnetization have been observed in Er/Fe and Tb/Fe multilayers respectively. The effects of the ion anisotropy and of the thickness of the layers are discussed.

FeIr(001) superlattices : growth, structure, and magnetic properties

The study of structures and magnetism of FeIr(001) superlattices leads us to observe three different cases. First, for Fe thicknesses up to 4 planes, Fe is of bct structure with an fcc Ni-like magnetic anisotropy. Second, for thick Fe layer, Fe is bcc and an antiferromagnetic coupling is observed. Third, for thin Ir layers, Ir is strained and plays an inportant role in magnetic behaviour.

Mössbauer measurements backscattering technique (CXMS) of laser irradiated cold forming tool steel (X210CR12)

Conversion x-ray Mössbauer measurements (CXMS) in backscattering technique are performed on a commercial cold forming tool steel (X210Cr12), subjected to single-pass laser irradiation. The structure of the affected layer is examined for laser powers ranging from 2700 W to 3050 W at different depths. The results of the spectra analysis are discussed in connection with Vickers hardness and metallographic data. If a complete molten layer is quenched, a high carbon content austenite is retained down to room temperature. This phase is mixed with some low carbon martensite and (Cr 0.5 Fe 0.5)> C3 carbide. The effects of carbon diffusion from the coating medium into the bulk are discussed. It is demonstrated that Mössbauer spectroscopy is a sensitive tool for phase analysis, including information about phase formation, and for delimiting the range of the quenched molten layer after laser treatment. It is thus a promising technique in this special kind of steel engineering.