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The effects of heat treatments in vacuum on magnetic permeability, Young's modulus and magnetoelastic wave amplitude were investigated in the amorphous ferromagnetic alloys Fe73.5Cu1Ta3Si15.5B7 and Fe73.5Cu1W3Si15.5B7 where tantalum or tungsten replaces niobium, which mas generally used with the same atomic fractions of the other elements. The stress sensitivity coefficient was also theoretically deduced in its development vs. the applied magnetic bias field. Structural relaxation and crystallization consequences are evidenced. Moreover an already predicted relation between the maximum of magnetoelastic wave amplitude and the minimum of stress sensitivity coefficient was confirmed.

The magnetic susceptibility during hysteresis cycles was measured in both amorphous and crystalline metallic ribbons. The analysis of the dependence on magnetizing field evidences a different behaviour due to the structural differences. The fundamental importance of the amplitude of the magnetizing field used for dynamic evaluation of initial susceptibility is demonstrated and related to the measured effects as well. Moreover, both temperature and frequency effects on the initial susceptibility confirm some peculiar properties related to the amorphous character.

Multilayered amorphous ribbons were produced by electrolytical deposition. They have exceptional magnetoelastic properties which enhance the amplitude of longitudinal magnetoacoustic waves travelling in the samples, also in comparison with similar-size ribbons of conventional metallic glass obtained by rapid quenching from the melt.

The high-frequency initial magnetic permeability and its relaxation have been studied in Fe62.5Co6Ni7.5Zr6Cu1Nb2B15 after heat treatment (both in furnace or via DC Joule heating). The magnetic permeability steadily increases in correspondence of both structural relaxation and nanocrystallisation of the alloy. The intensity of the permeability relaxation (measured between fixed times after demagnetisation) is reduced by structural relaxation but exhibits a sharp maximum immediately before the onset of nanocrystallisation. The nanocrystalline alloy is characterised by a nonzero, if reduced, permeability relaxation.

We have produced ribbons of Co1-xPx (x almost-equal-to 0.09) with the coexistence of microcrystalline and amorphous structure. These kind of materials have different magnetic and magnetostrictive behaviour in comparison with that already known of crystalline or amorphous specimens (x almost-equal-to 0.05 and 0.12, respectively). In particular we demonstrate the obtaining of good magnetoelastic response and, at the same time, the results validate the structure sensitivity of resonant magneto-acoustic waves. The complete behaviour of wave amplitude as a function of the applied magnetization field is compared for each sample and explained.

The piezomagnetic coupling coefficient (the <>) is quantitatively investigated below room temperature and a comparison is made among polycrystalline samples and amorphous ones. The technique used is an original one. It experimentally consists in the measurement of the amplitude of magnetoelastic waves, their resonance frequency and differential susceptibility; theoretically, it consists in coupling Newton's law of force with the piezomagnetic state equations. The results clearly show different responses of polycrystalline samples with respect to the amorphous ones; in particular the nonmonotonic behaviour of the <> for metallic glasses is interesting for establishing their actual magnetic states at low temperature.

The actual knowledge on Co-P electrodeposited alloy is reviewed. The differences among the experimental conditions of production, and their influnce on the obtained material as well, are discussed. Recent results both in microcrystalline layers and in amorphous multilayers are reported. In particular the attainment of not-trivial magnetoelastic properties is emphasized.

Mossbauer spectra, susceptibility and magnetization measurements were performed on Fe 40 Ni 40 P 14 B 6 amorphous ribbons. The results indicate the existence of correlated ferromagnetic regions of different sizes. With decreasing temperature a collective freezing of the resulting moments occurs with cluster-glass-like characteristics.

Measurements of the initial permeability as a function of tensile stress were performed in cw-laser annealed metglas 2826 (50 μm ribbon). The results indicate the possibility of decreasing the magnetization at a very low field by means of an appropriate applied tension. The dependence of the magnetostriction curves and the magnetoelastic wave amplitude on the tensile stress supplies experimental evidence of the above mentioned prediction. On the basis of current understanding of the inhomogeneous mode of deformation, an explanation of the observed effects is proposed Mesure de la permeabilite magnetique initiale des rubans de 50 μm d'epaisseur recuits par laser continu en fonction de la traction. L'aimantation peut etre reduite. Courbes de magnetostriction et amplitude de l'onde magnetoelastique. Explication par un mode inhomogene de deformation

C.w. laser annealing of metglas 2826 ribbons was performed by varying beam power and irradiation time. A simplified thermal model was elaborated to have information about the temperature rise of the samples and the occurrence of crystallization. The predictions were in agreement with the experimental results. The laser-induced changes of magnetic and mechanical properties were particularly tested by means of the magnetostrictive response and the Young-modulus variations.

The magnetization changes, ΔM, induced by an external tensile stress, σ, in metallic-glass ribbons are theoretically calculated starting from the simplified model generally used for describing the magnetoelastic coupling in amorphous metals. Taking into account the discrepancies between the ideal behaviour and the real one as revealed in commercial amorphous ribbons, we show that the experimental results, concerning ΔM as a function of σ, can be well predicted by the theoretical evaluations. On the other hand, it results that a suitable ferromagnetic ribbon can be a magnetoelastic sensor able to measure variations of ≃1 MPa up to the 100 MPa stress.

The as quenched amorphous ribbons are in a metastable condition and need a thermal treatment to relax internal stresses and/or to induce magnetic anisotropy. The evaluation of the results of various annealing treatments of the alloy Metglas 2826 was performed by magnetic measurements and Mossbauer spectroscopy, for the characterization of structural relaxation, easy magnetization axis changes and transition to crystalline order. Heat treatments considered include conventional (batch), laser and magnetic annealing (in transversal field).

A new metallic glass alloy characterized by high amplitude of magnetoelastic waves was synthesized. X-ray spectra evidenced the amorphous structure in the as-cast material, while differential thermal analysis confirmed the metastable initial phase and the occurrence of several crystallization peaks. The alloy shows a high difference between the glass transition and crystallization temperatures. Several heat treatments were performed and the structural relaxation effects were shown by means of the behavior of magnetization, Curie temperature and the resonant magneto-elastic wave amplitude. The strong increase of the last parameter, induced by the occurrence of the amorphous structure, is the most important result for application. Magnetic and magneto-elastic properties deteriorate if crystallization occurs, but in the optimal condition a partial nanocrystallisation may be present.