Effect of surface domain structure on wall mobility in amorphous microwires

摘要

Recently reported results on domain wall propagation within the inner core of bistable Fe-based positive magnetostrictive amorphous microwires opened up the way for future spintronic applications of amorphous microwires. Domain wall propagation has also been investigated in Co-based nearly zero magnetostrictive microwires, which become bistable under certain conditions. Wall velocity and mobility values were found to be superior in the latter type of microwires due to their much smaller magnetoelastic anisotropy. In this paper, the key role played by the surface domain structure of microwires in determining the wall mobility is investigated. Wall velocity measurements have been performed on (Co_(0.94)Fe_(0.06))_(72.5)Si_(12.5)B_(15) microwires in as-cast glass-coated state and after glass removal with a hydrofluoric acid solution. Surface magnetization has been studied employing magneto-optical Kerr effect. The results show that both as-cast glass-coated microwires and microwires with the glass coating removed, which are bistable, display a helical magnetization in the surface region. The direction of the magnetization in this region affects the mobility of the propagating wall due to the stray fields associated with the preponderant components of the magnetization.