Influence of Thermal Treatment on Frequency Dependence of the Switching Field in Amorphous and Nanocrystalline FeNiMoB Microwires

Amorphous and nanocrystalline ferromagnetic glass-coated microwires show excellent magnetic properties that make them very suitable to be employed as sensing elements in devices for technical applications. New $Fe_{40}Ni_{38}Mo_4B_{18}$ alloy composition can be appropriate to prepare soft magnetic nanocrystalline microwires which exhibit magnetic bistability even in the nanocrystalline state. Stability of magnetic properties after different thermal treatments ($T_{a}$ = 250-425°C) and after nanocrystallization was confirmed by the switching field $H_{sw}$ measurements. The frequency dependence of the switching field was investigated. Two contributions to the domain wall switching mechanism were recognized: magnetoelastic one coming from the magnetoelastic interaction of the magnetic moments with the stresses and relaxation one coming from the structural relaxation of local defects at atomic scale. But, the relative role of both contributions has been shown to vary strongly in different stage of devitrification.