Tailoring circular magnetic domain structure and high frequency magneto-impedance of melt-extracted Co69.25Fe4.25Si13B13.5 microwires through Nb doping

Abstract

The surface roughness, surface magnetic domain structure (SMDS), and high frequency magneto-impedance (MI) response of melt-extracted Co69.25Fe4.25Si13B13.5 microwires with 1 at.% Nb substitution for B have been studied by atomic force microscopy (AFM), magnetic force microscopy (MFM), and impedance analyzer, respectively. We show that the Nb doping significantly increases the domain width from 729 to 1028 nm, while preserving the low surface roughness (∼2 nm) of the base composition. As a result, a greater improvement of the high frequency MI response (∼300%/Oe at 20 MHz) is achieved in the Nb-doped microwire. A well-defined circumferential anisotropy formed with Nb-substitution is key to a highly sensitive MI field sensor.