Size triggered change in the magnetization mechanism of nearly zero magnetostrictive amorphous glass-coated microwires

Results on the change in the magnetization mechanism with microwire dimensions in nearly zero magnetostrictive Co-based amorphous glass-coated microwires are reported. Microwires with a metallic core diameter of 20 μ m or more display a change in the magnetization mechanism from domain wall displacement to magnetization rotation with the increase of an externally applied tensile stress, which is equivalent to an increase of the glass coating thickness. Microwires with the metallic core diameter below 20 μ m do not display this change in the magnetization mechanism. They are magnetized only through magnetization rotation. Experimental results are explained based on the competition between magnetostatic and magnetoelastic energy terms. Minimization of a preponderant magnetostatic term in the total free energy results in an axial easy axis of magnetization and a corresponding bistable magnetic behavior. Bistability vanishes if the magnetoelastic energy term becomes preponderant and the corresponding easy axis becomes transverse. A reasonable estimation of the magnetostatic energy density in Co-based microwires has been obtained based on hysteresis loop measurements with the applied tensile stress as a parameter.