Domain Wall Propagation in Co-Based Glass-Coated Microwires: Effect of Stress Annealing and Tensile Applied Stresses

Abstract

RECENTLY, domain wall (DW) propagation in magnetic wires has been recognized as one of the important lines of research due to its potential use in magnetic devices [1]–[7]. The DW speed and the possibilities for the DW dynamics manipulation are quite relevant for these applications. Extremely fast DW propagation has been reported for amorphous magnetically bistable microwires with positive magnetostriction constant λs and circular cross section (usually, exceeding 1000 m/s) [3], [4]. On the other hand, ferromagnetic glass-coated microwires have attracted growing attention in the last few years, mostly owing to their outstanding soft magnetic properties (magnetic bistability, enhanced magnetic softness, Giant magnetoimpedance (GMI) effect, and fast DW propagation) [5]–[7]. These microwires have a composite character consisting of a cylindrical metallic nucleus of (1–30 μm) and glass coating (with thickness of 1–20 μm). These microwires can be prepared by the modified Taylor–Ulitvosky technique, which involves simultaneous rapid quenching and drawing of the metallic nucleus inside a glass capillary [6], [7]. Thus, strong stresses are introduced in the metallic nucleus arising from the drawing and quenching, as well as from the different thermal expansion coefficient between the glass sheath and the metallic nucleus [5], [6], [8]–[10]. Therefore, the magnetoelastic anisotropy induced by the internal stresses plays an important role in controlling their magnetic properties [4], [5], [7]–[9]. Fe-rich microwires with positive magnetostriction coefficient, λs , present magnetic bistability related to a large and single axially magnetized inner core. Therefore, one can observe quite fast magnetization switching within the single magnetic domain related with fast DW propagation. In particular, these materials are unique for studying the DW propagation since they can exhibit a very fast DW velocity [2]–[4], [6], [11]. On the other hand, it is well known that the DW dynamics in glasscoated microwires is strongly dependent to external parameters