Nearly zero magnetostrictive glass-coated amorphous microwires are suitable materials for sensor applications. Samples with metallic core diameters below 20 [.proportional]m exhibit almost nonhysteretic BH loop, related to the existence of a domain structure with azimuthal easy axis. The magnetic behavior of these microwires is changing drastically when the metallic core diameter increases over 25 [.proportional]m, i.e. they display a bistable magnetic behavior at low fields, that is a one step magnetization reversal at a certain value of the applied field, called switching field. Results on the direct domain observation in nearly zero magnetostrictive Co68.25Fe4.5Si12.25B15 glass-coated amorphous microwires by means of Kerr microscopy are reported for the first time. The effect of glass removal on the domain structure has been also studied. AC hysteresis loop measurements have been employed to establish a correlation between domain structure and magnetic behavior.
Glass-coated microwires exhibit a single domain configuration with the magnetization pointing mostly to the wire axis. The domain structure does not change qualitatively after glass removal, but the parameters of the squared hysteresis loops are modified. The remanence to saturation ratio increases after glass removal, while the switching field decreases.
The obtained results are of interest for sensor applications, and show that the metallic core diameter is a dimensional factor that contributes to important changes in the domain structure and magnetization process of such microwires.