Search

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 welldefined circumferential anisotropy formed with Nb-substitution is key to a highly sensitive MI field sensor. [ABSTRACT FROM AUTHOR]

A small DC magnetic field can induce an enormous response in the impedance of a soft magnetic conductor in various forms of wire, ribbon, and thin film. Also known as the giant magnetoimpedance (GMI) effect, this phenomenon forms the basis for the development of high-performance magnetic biosensors with magnetic field sensitivity down to the picoTesla regime at room temperature. Over the past decade, some state-of-the-art prototypes have become available for trial tests due to continuous efforts to improve the sensitivity of GMI biosensors for the ultrasensitive detection of biological entities and biomagnetic field detection of human activities through the use of magnetic nanoparticles as biomarkers. In this review, we highlight recent advances in the development of GMI biosensors and review medical devices for applications in biomedical diagnostics and healthcare monitoring, including real-time monitoring of respiratory motion in COVID-19 patients at various stages. We also discuss exciting research opportunities and existing challenges that will stimulate further study into ultrasensitive magnetic biosensors and healthcare monitors based on the GMI effect.