The surface magnetization processes taking place in simple permalloy (Py) and FeGa nanowires, Py/Cu, CoFeB/Cu, CoNiP/Cu, FeGa/Py, and FeGa/CoFeB multilayered nanowires have been studied by magneto-optical Kerr effect (MOKE) magnetometry. The results indicate a strong correlation between the direction of the anisotropy axis relative to the direction of the applied field and the plane of incidence of the laser spot, as well as the effect of dipolar interactions between the nanowires or between the ferromagnetic layers on the magnetization reversal. The larger laser spots are inducing more noise in the MOKE hysteresis loops because of the dimensional imperfections along the nanowires.

Results on the preparation and magnetic characterization of rapidly solidified amorphous glass-coated nanowires are reported. Rapidly solidified nanowires have been investigated by means of bulk and surface hysteresis loop measurements, scanning electron microscopy, and ferromagnetic resonance. Domain wall velocity has been measured to demonstrate the suitability of the new nanowires for spintronic applications. Changes in composition, in the thickness of the glass coating, and nanowire dimensions allow extensive tailoring of the domain wall mobility.

Results on the magnetic behavior of glass-coated amorphous wires with metallic nucleus diameters in the submicron range are reported for the first time. The magnetic behavior of nearly zero magnetostrictive submicron amorphous wires is different from that observed in amorphous microwires with typical dimensions and similar composition. Submicron wires are bistable, whereas typical microwires show an almost anhysteretic loop. Bistability of submicron wires is maintained even in a very thin surface layer, which was shown to display a helical magnetic anisotropy. The origin of this specific behavior is the shape anisotropy which becomes dominant at lower dimensions of the metallic nucleus. The study of submicron amorphous wires opens up the way for new applications of amorphous wires.

Rapidly solidified submicron amorphous wires with positive and nearly zero magnetostriction are studied in order to understand the effect that a significant reduction in the diameter of the metallic nucleus has on their magnetic behavior and anisotropy distribution. Submicron wires with metallic nucleus diameters between 350 and 800 nm were investigated with hysteresis loop measurements, the magneto-optical Kerr effect, and ferromagnetic resonance studies. The analysis of the results shows the dominant role of shape anisotropy in nearly zero magnetostrictive submicron wires, as well as in positive magnetostrictive ones with nucleus diameters smaller than 350 nm. Magnetoelastic anisotropy is still important in positive magnetostrictive submicron wires with metallic nucleus diameters larger than 500 nm.

Fe_79.7−xNb_0.3Cr_xB₂₀ (x = 11.5–13.5 at. %) submicron powders with glassy structure and sizes between a few tens of nm and 1 μm have been prepared by high-energy ball milling from glassy melt-spun ribbons (MSRs) precursors. The glassy structure existing in the MSRs, and consisting of Fe-Cr clusters embedded within the (Fe,Nb)₃B residual amorphous matrix, is preserved by milling the annealed MSRs in oleic acid and n-heptane. The glassy structure of the submicron powders confers the specific magnetic properties and allows tuning the Curie temperatures in the range of 15–50 °C. The precipitation of α-Fe in excess shifts the Curie temperature to 780 °C. The use of surfactants (oleic acid or heptane) avoids partially the agglomeration of powders, and their individual size goes down to 25–40 nm. The heating efficiency of the submicron powders in a.c. fields (H = 350 mT and f = 153 kHz) evidences a working regime in the range of 33–45 °C, depending on Cr content, indicating the suitability of using the Fe-Cr-Nb-B powders for hyperthermia applications.