Amorphous and nanocrystalline glass-coated wires: Optimization of soft magnetic properties

Abstract

In this chapter, we are reporting on engineering of soft magnetic properties, Giant magnetoimpedance (GMI) effect and domain wall dynamics of amorphous and nanocrsytalline glass-coated microwires. We overview the effect of magnetoelastic anisotropy that can be controlled through the strength of the internal stresses or the metallic alloy composition on the GMI effect and magnetic softness of glass-coated microwires. High GMI effect has been observed in as-prepared and annealed amorphous Co-rich microwires with vanishing magnetostriction coefficient. Selection of the appropriate chemical composition and geometry allows achievement of high GMI effect. Magnetic properties of amorphous microwires are strongly affected by the annealing. In Co-rich microwires after annealing rectangular hysteresis loops and coexistence of GMI effect and fast domain wall propagation can be observed. Observed changes are discussed considering effect of annealing on the magnetostriction coefficient. Similarly in Fe-rich microwires annealing affects the DW dynamics. Investigations of magnetic properties of Finemet-type Fe-Cu-Nb-Si-B microwires reveal that annealing considerably affects the hysteresis loops and GMI effect of this family of microwires. Magnetoelastic anisotropy affects soft magnetic properties of as-prepared FeCuNbSiB microwires. We observed magnetic softening and a considerable increasing of the GMI effect in Finemet-type FeCuNbSiB with nanocrystalline structure. After an adequate annealing of Finemet-type microwires we observed a GMI ratio of about 100%. In Hitperm-like Fe38.5Co38.5B18Mo4Cu1 microwires rectangular hysteresis loops and fast domain wall dynamics have been observed. Developed magnetically soft thin wires with optimized GMI effect are suitable for magnetic sensors applications.