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.
Highlights
IntroductionSoft ferromagnetic materials (wires, ribbons, and thin films) exhibiting giant magneto-impedance (GMI) effect are promising for high performance magnetic sensor applications.[1,2,3,4] It has been reported that GMI sensors operate at room temperature, with ultrahigh sensitivity, high thermal stability, high spatial resolution, small size, light weight, and low power consumption.[5] A wide range of products such as portable gauss meters and smart phones utilizing Co-rich amorphous wire based GMI sensors have been developed by the Aichi Steel Company - Japan and are available in markets.[6] Recently, there has been growing interest in developing GMI materials and sensors that can operate at high frequencies up to 1 GHz.[7,8,9,10] Melt-extracted amorphous microwires of composition Co69.25Fe4.25Si13B13.5 have emerged as attractive candidates for low-field high sensitivity GMI sensors, most work has been limited to a frequency range below 20 MHz.[11,12,13] Despite our recent studies,[14,15] a clear understanding of high frequency GMI and its correlation with the surface magnetic domain structure (SMDS) of melt-extracted microwires is still lacking
Soft ferromagnetic materials exhibiting giant magneto-impedance (GMI) effect are promising for high performance magnetic sensor applications.[1,2,3,4] It has been reported that GMI sensors operate at room temperature, with ultrahigh sensitivity, high thermal stability, high spatial resolution, small size, light weight, and low power consumption.[5]
Atomic force microscopy was conducted on the various microwires before magnetic force microscopy (MFM) images were taken
Summary
Soft ferromagnetic materials (wires, ribbons, and thin films) exhibiting giant magneto-impedance (GMI) effect are promising for high performance magnetic sensor applications.[1,2,3,4] It has been reported that GMI sensors operate at room temperature, with ultrahigh sensitivity, high thermal stability, high spatial resolution, small size, light weight, and low power consumption.[5] A wide range of products such as portable gauss meters and smart phones utilizing Co-rich amorphous wire based GMI sensors have been developed by the Aichi Steel Company - Japan and are available in markets.[6] Recently, there has been growing interest in developing GMI materials and sensors that can operate at high frequencies up to 1 GHz.[7,8,9,10] Melt-extracted amorphous microwires of composition Co69.25Fe4.25Si13B13.5 have emerged as attractive candidates for low-field high sensitivity GMI sensors, most work has been limited to a frequency range below 20 MHz.[11,12,13] Despite our recent studies,[14,15] a clear understanding of high frequency GMI and its correlation with the surface magnetic domain structure (SMDS) of melt-extracted microwires is still lacking
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