G. Fratucello

Magnetic properties of Fe/Cu multilayers

Abstract Fe/Cu multilayers have been prepared under high vacuum conditions. The thickness of the Fe layer is about 5 A while the thickness of the Cu layer is 50 A. A complete study of the magnetic properties have been performed by using a SQUID magnetometer and CEMS. The sample shows a very rich behavior in the low applied field regime. The coexistence of different interactions seems to be present.

Static magnetization direction in fcc (111) Fe/Ni multilayers

Abstract The rotation of the static magnetization was measured by Mossbauer spectroscopy as 2.5 monolayers of resonating 57 Fe were moved from inside the Fe films to the Fe/Ni interfaces in Fe/Ni (17/200 A) multilayers produced by thermal evaporation. The results indicate a remarkable dependence of the tilt angle as a function of distance from the surface.

Ferromagnetism of fcc iron films grown on nickel

Abstract Polycrystalline multilayers of Fe-Ni produced by thermal evaporation are studied; some results obtained by a vibrating sample magnetometer, Mossbauer spectrometer and X-ray diffractometer are reported and discussed. Fe seems to grown on Ni with fcc structure. Fe atoms at the Ni/Fe interface seem to have localizated magnetic moments depending on the crystallographic orientations of the grains of the substrate; the remaining Fe atoms between the two interfaces appear as highly susceptible metal.

Mössbauer spectroscopy of amorphous Fe–Si–B alloys with different free volume content

The hyperfine field distributions of as‐cast and annealed Fe81.5Si4B14.5 amorphous alloys prepared with different quenching rates have been measured at room temperature by means of Mossbauer spectroscopy. No significant differences have been found between the spectra of as‐cast materials produced at different quenching rates, in contrast with the results of measurements of the electrical resistivity and the magnetic permeability aftereffect. This result indicates that the variation of the distribution of pressure–density fluctuations in differently quenched systems does not modify the value of the hyperfine field, which is rather dominated by the effect of the local magnetic disorder, and not substantially influenced by small variations of the quenching rate. The hyperfine field distributions of annealed ribbons are coherently shifted towards higher values with respect to the ones of as‐cast alloys. This result is related the increase of the Curie temperature, observed in these alloys after annealing, and...

Structural and magnetic properties of Ni/γFe/Ni multilayers

Abstract The crucial point in the characterization of magnetic interfaces is the knowledge of the morphology and the structure of the films. Ni/γ Fe/Ni multilayers were grown on three different buffer layers. Structure and morphology were investigated by X-ray diffraction and scanning tunneling microscope. Mossbauer spectroscopy was used to provide local information on both structure and magnetism of the buried Fe layers.

The Ni-γ-Fe interface: hyperfine magnetic field and magnetic anisotropy

Abstract Conversion Electrons Mossbauer Spectroscopy (CEMS) is used to study the magnetic polarization state and the magnetic anisotropy of ultrathin Fe/Ni films in multilayer samples with two, one and any Fe/Ni interface. The analysis of the distribution function of the hyperfine fields indicates a magnitude of 34 T for the Fe/Ni interface field and gives evidence of the existence of a pure, highly susceptible γ-Fe phase. Results corresponding to intermixed regions suggest enhanced hyperfine fields and magnetic moments in local environments with more than 6 and up to 9 nearest Fe neighbor atoms, and low fields in Fe sites with 10–11 Fe neighbors. Out-of-plane perpendicular anisotropy is found only in samples having an Fe/Ni interface.

Magnetic properties of (111) Cu/Fe multilayers

The magnetic properties of (111) Cu/Fe multilayers grown on Cu underlayers of several thickness (2000-500-50 Å) on cleaved mica have been investigated by Mössbauer spectroscopy and SQUID magnetometry. The analysis of experimental results suggests that 2.5 monolayers of ψ-Fe interfaced with Cu evolves partially from paramagnetic to ferromagnetic states as the Cu underlayer thickness is reduced to 50 Å and partially from weak to strong antiferromagnetism.

Study of the Fe−Ni interface by conversion electron Mössbauer spectroscopy

Nickel-gamma iron interfaces obtained by growing films of Fe on Ni substrates are studied using CEMS. We have found that a) intermixing is confined to two atomic layers, b) Fe atoms deposited on structural defects of the Ni (111) surfaces are magnetically polarized, c) Fe epitaxially grown on Ni is highly susceptible at room temperature. Moreover the Ni−Fe interface shows Neel-type magnetic anisotropy.

Magnetic hyperfine field of Fe interfaced with Ni, Cu, Ni/Cu, and Cu/Ni

Abstract Thin films grown in 10 -6 Torr on polycrystalline substrates of Ni, Cu, Ni/Cu, and Cu/Ni are investigated by transmission Mossbauer spectroscopy at 300 K. The effect of the substrate on the structure of the Fe films is discussed. Fe films grown on Ni seem to assume fcc structure while those on Cu are bcc.

MOSSBAUER SPECTROSCOPY OF (111) GAMMA -FE SINGLE LAYERS GROWN ON NI

The magnetic profile of Ni(111)/γ-Fe/Ni with different thickness is studied by CEMS Mössbauer spectroscopy. It depends both from the thickness of the Fe layer and the roughness of the (111)Ni surface. For a particular thickness of 8 Å, two magnetic regions have been pointed out, one antiferromagnetic with low spin states and the second ferromagnetic with high spin states.