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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 role of magnetoelastic energy to determine the causes which affect the magnetic anisotropy are reviewed. The simple model used to describe magnetostriction in the new nanostructured materials is reported. Starting from this model the magnetostriction in multilayer samples, of the kind magnetic material/non-magnetic material, is discussed. In particular the fundamental influence of the interlayers is shown. Finally it is demonstrated that by measurement of saturation magnetostriction it is possible to have information on the interlayers thickness and average composition.

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.

A previos thermal model for the heat treatment of a little metal ribbon, moving under a broad laser beam with Gaussian intensity distribution, is elaborated in order to apply it also in the opposite experimental condition, namely for sample width higher than the laser spot. The temperature value vs. the distance from the symmetry axis of the treated zone is determined as a function of both the sample displacement rate and the laser power. When structural and magnetic-property modulation is produced in the transverse direction of a glassy metal ribbon, the experimental results, concerning both reduced magnetization as a function of the temperature and structure changes, are in agreement with the thermal-model predictions.

Interaction between acoustic field and electromagnetic field, in a magnetostrictive ferromagnetic material produces both transversal quasiacoustic waves (QACW) and quasielectromagnetic waves (QEMW) named hybrid waves. Properties of hybrid waves have been studied and their dependence on conductivity has been emphasized in the piezomagnetic case. To this end, the system of Maxwell’s equations, Newton’s law of force, and piezomagnetic state equations were solved for an infinite continuous medium. It is shown that for a particular conductivity value σc, the hybrid modes coincides in a mixed propagation mode we called MHWM. The dispersion relation, in the case of separate hybrid waves, as well as in the mixed mode MHWM, is discussed. The MHWM has a velocity Vc, which is independent of wave number k. Moreover we point out that (a) for very high σ, the QEMW velocity reaches a k‐independent value while the QACW velocity falls to zero, (b) the behavior of σc(k), at constant Vc, is linear, (c) for σ≠σc, at constant...

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.

A contribution to the investigation of the stress effect on the saturation magnetostriction of polyerystalline rods stressed by torsion is presented. The critical torsional stress above which magnetostriction remains constant is found and the crystal anisotropy level, at various torsions, is estimated. As in the tensional case, the effect of crystal anisotropy at the critical stress has not been clearly interpreted so far. A study of the behaviour of the magnetization curve near saturation provides a possible explanation.

Magnetoelastic wave amplitude, a, was measured vs. the temperature during thermal cycles in Metglas 2826. When the Curie temperature, T C, has been reached, the A value vanishes due to the fall of the magnetoelastic coupling in the paramagnetic state. This allows evaluation of the T c temperature. The latter increases after the iterated thermal treatments while the magnetic anisotropy K u decreases. Also the A amplitude, measured at room temperature after the subsequent thermal treatments, shows an increasing behaviour. The values of K u, T c and A approach saturation after the same number of thermal cycles; this suggests that the structural relaxation produced by annealing is the microscopic mechanism governing all the three physical quantities. In particular we explain the connection between K u and A by means of the longitudinal magnetostriction.

The thermal model describing the c.w.-annealing of ribbon-shaped materials irradiated by a moving laser beam has been revised and imrpoved. New experimental results on the initial permeability of annealed metallic glasses are presented. © 1983 Società Italiana di Fisica.

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 anisotropy induced by magnetic annealing in a transversal field is correlated with the Young modulus, the longitudinal magnetostriction and the magnetoelastic coupling coefficient. Subsequently it is shown that the value of the anisotropy deriving from directional short-range ordering,kDSRO, can be calculated in an original manner by means of the mentioned parameters. ThiskDSRO evaluation is in increasing agreement with its directly measured value, when the magnetic-annealing effects approach saturation. The magnetic heat treatment influences can be described by a small rise of the internal stress, in comparison with conventional annealing, and a large increase of longitudinal magnetostriction.

The Young modulus dependence on thermal treatment and magnetization state was analysed on various metallic glasses. Propagation of standing magnetoelastic waves was used as an investigation technique. A simple model was elaborated to predict the magnetoelastic coupling. The explanation of the results was suggested on the basis of macroscopic and microscopic relaxation effects and is also revealed by the measurement of internal friction and magnetoelastic-coupling constant.

The initial development of the transverse anisotropy induced by magnetic annealing is investigated for magnetizing field values which are much smaller than the ones generally employed. Measurements of Young modulus and longitudinal magnetostriction not only show their relation with induced anistotropy, as predicted in a previous paper, but also enable us to calculate the easy magnetization direction. The results are in agreement with the distributed relaxation time theory.