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Magnetic energy losses and permeability have been investigated in laboratory prepared and commercial Mn–Zn sintered ferrites from quasi-static conditions up to 10 MHz. The mechanisms leading to energy dissipation, either due to domain wall displacements or magnetization rotations, have been quantitatively assessed and their respective roles have been clarified. Domain wall processes dissipate energy by pure relaxation effects, while rotations display resonant absorption of energy over a broad range of frequencies. Their specific contributions to the permeability and its frequency dispersion are thus identified and separately evaluated. It is shown that eddy currents are always too weak to appreciably contribute to the losses over the whole investigated frequency range and that rotations are the dominant magnetization and loss producing mechanisms on approaching the MHz range, as predicted by the Landau–Lifshitz–Gilbert equation with distributed anisotropy fields.

Two series of rapidly solidified FINEMET (Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 ) alloys with and without partial substitution of Al (1.5 at%)/Ge (1 at%) were prepared by melt-spinning technique. The nanocrystallization process was carried out by the heat treatment of the as-spun ribbons at 560 °C for 1 h in a vacuum furnace. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimeter (DSC), Mossbauer spectroscopy, and magnetoimpedance (MI) measurements were conducted on the as-quenched and heat-treated alloys to investigate their structural and magnetic properties. The average crystallite sizes obtained for the heat-treated samples were in the range of 10–12 nm as confirmed by our XRD and TEM data. The ultrasoft magnetic behavior observed for the Al/Ge-substituted nanocrystalline alloys was confirmed both by our magnetic data and magnetoimpedance ratio (MIR%) results. A twofold increase in the magnitude of the MIR% (99%) was observed for the Al/Ge-substituted nanocrystalline alloy against that of the pure FINEMET alloy (∼48%) measured at 5.5 MHz. This is believed to be related to the decrease of the magnetocrystalline anisotropy as well as magnetostriction decline due to the Al substitution for Fe atoms in this nanostructured alloy.

Magnetic flux density standards traceable to the SI units have been developed at IEN-INRIM, by which dissemination for general measurement and testing activities can be pursued. The reference system covers a range of values extending from μ 0 H ∼ 1 T to μ 0 H ∼ 10 μ T and is centered on the use of NMR magnetometers, calibrated coils, and stable current sources. The relative measuring uncertainty of the system is shown to increases with decreasing the field strength value and it is estimated to range between a few 10 - 6 and some 10 - 3 .

The magnetisation process has been investigated in thin Ni sheets by means of fluxmetric and alternating force techniques. As-rolled samples exhibit a rotation-dominated reversible magnetisation process, related to stress-induced and magnetocrystalline anisotropies. After annealing the rotations combine with substantial reversible displacements of the domain walls. It is always found that the transverse reversible susceptibility passes through a maximum at a field of the order of the anisotropy field.

The role of coherent moment rotations on the magnetization process of soft amorphous alloys has been investigated in theory and experiment. In particular, a theoretical formulation for the reversible magnetization curve has been worked out by modeling the spatial distribution of the magnetization in ribbon-shaped samples and its evolution under an applied field. Such a distribution is assumed to derive from the combined effects of frozen-in random anisotropies and the macroscopic in-plane anisotropy. Experiments are reported concerning Fe-based alloy ribbons, where a range of macroscopic anisotropy values are achieved through the application of a variable tensile/compressive stress. In order to determine the reversible component of the magnetization curve I rev ( H ) a method is devised that exploits the susceptibility after-effect, which permits one to discriminate between contributions from coherent spin rotations and domain wall displacements. The so obtained I rev ( H ) curve and its dependence on stress are found to agree with the theoretical prediction.