Controlling depinning and propagation of single domain-walls in magnetic microwires

Abstract

The magnetization reversal in magnetostrictive amorphous microwires takes place by depinning and propagation of a single domain wall. This is a consequence of the particular domain structure determined by the strong uniaxial anisotropy from the reinforcement of magnetoelastic and shape contributions. In the present study, after an overview on the current state-of-the art on the topic, we introduce the general behaviour of single walls in 30 to 40 cm long Fe-base microwires propagating under homogeneous field. Depending on the way the walls are generated, we distinguish among three different walls namely, standard wall, DW _st , depinned and propagating from the wire’s end under homogeneous field which motion is the first one to switch on; reverse wall, DW _rev , propagating from the opposite end under non-homogeneous field, and defect wall, DW _def , nucleated around local defect. Both, DW _rev and DW _def are observed only under large enough applied field. In the subsequent section, we study the propagation of a wall under applied field smaller than the switching field. There, we conclude that a minimum field, H _dep,0, is needed to depin the DW _st , as well as that a minimum field, H _prop,0, is required for the wall to propagate long distances. In the last section, we analyse the shape of induced signals in the pickup coils upon the crossing of the walls and its correlation to the domain walls shape. We conclude that length and shape of the wall are significantly distorted by the fact that the wall is typically as long as the measuring coils.