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Reversible and irreversible magnetization processes have been investigated in thin Ni sheets by means of flux-metric and alternating-gradient-force magnetometer techniques. Cold-rolled samples exhibit a rotation-dominated process at low fields, and the value of the associated susceptibility, related to the stress-induced and the magnetocrystalline anisotropies, can provide an estimate of the residual stress in the material. Reversible displacements of the domain walls come into play and combine with rotations in the annealed samples. A method is devised, by which domain-wall and rotational contributions to the reversible susceptibility can be singled out. The Rayleigh law always accounts for the behavior of hysteresis loops and losses at low fields, but rotations engender some peculiar evolution of the related parameters and their relationship with the coercive field. Magnetic softening by stress relief is assessed, as a whole, through Preisach analysis. It is found that the local stochastic coercive fiel...

Rotational and alternating hysteresis losses have been investigated in theory and experiment in nonoriented soft magnetic laminations. Attention has been focused on the dependence of energy loss on peak magnetization Ip. The experiments, performed in a wide induction range (∼2×10−4 T≤Ip≤∼1.6 T), show that the ratio between rotational and alternating energy losses Whr/Wha is a monotonically decreasing function of Ip. A quantitative theoretical investigation is carried out through modeling of the magnetization process under rotating field and its relation to processes under alternating field. Three basic mechanisms of magnetization rotation are considered: linear combination of unidirectional hysteresis loops at low inductions (Rayleigh region), cyclic rearrangement of magnetic domains between different easy directions at intermediate inductions, and coherent spin rotation toward the approach to magnetic saturation. The ensuing predicted behavior of Whr/Wha is found to be in good agreement with the experime...

The role of stress‐induced anisotropy on magnetic power losses has been investigated in FeBSiC amorphous ribbons, in the ‘‘as‐quenched’’ state and after annealing. Loss separation has been accomplished up to 400 Hz, under a wide range of applied tensile stresses (3.5 MPa≤σ≤300 MPa). It is found that, by increasing σ, the hysteresis loss component Wh is initially decreased and passes through a minimum around a critical stress σ0. Correspondingly, rearrangement of the maze domain structure associated with the unstressed state occurs and a longitudinally oriented pattern sets in. The dynamic loss exhibits a somewhat opposite trend, as it tends to monotonically increase with σ, thus attenuating the overall benefits of tensile stressing. Insight on the physical mechanisms responsible for these phenomena is obtained by measuring, at different stress levels, Wh versus temperature (20 °C≤T≤280 °C). Topological rearrangements of the domain structure and interaction of the Bloch walls with localized stress fluctuat...

We investigate the role of grain size in the magnetization process of nonoriented 1.7% Al 1.9% Si Fe steels by measuring the power spectrum and the amplitude probability distribution of the Barkhausen noise. Experiments refer to single strips of variable grain size (0.03 mm

The results of our investigation on current noise in aluminum films are pointed out. They were not intended as a check of Hooge and Hoppenbrouwers’s theory.