Magnetoimpedance effect assisted by current-driven transverse domain formation.

Magnetic field sensors based on the magnetoimpedance (MI) effect are attracting increasing attention for next-generation healthcare, environmental monitoring, industrial automation, and wearable electronic systems because of their exceptional sensitivity and rapid response to weak magnetic fields. However, achieving high-performance and miniaturized MI sensors requires precise control of magnetic domain structures and anisotropy, particularly in microscale magnetic conductors. Here, we demonstrate a current-assisted strategy for enhancing the MI effect through transverse domain engineering in amorphous Fe-Si-C microwires with widths ranging from 250 down to 40 µm. By combining laser-assisted microfabrication, magnetic characterization, impedance measurements, and MuMax3 micromagnetic simulations, we systematically reveal how geometric confinement and direct-current (DC) bias cooperatively regulate domain evolution and transverse magnetization dynamics. The results suggest that reducing the microwire width strengthens shape anisotropy, suppresses demagnetizing effects, and promotes the formation of refined stripe-like and helical magnetic domains. Under a DC bias, the induced circumferential magnetic field further enhances transverse magnetic permeability, significantly amplifying the MI response. Notably, the narrowest microwire of 40 µm exhibits a maximum MI ratio of 26.7% under a 70 mA bias current, more than double its unbiased value and significantly higher than the ratio observed in wider microwires. Micromagnetic simulations reveal that current-induced helical domain formation and enhanced transverse magnetization are the key mechanisms responsible for the observed performance improvement. In addition, the optimized microwires demonstrate enhanced field sensitivity and angular response, highlighting the important interplay between shape anisotropy and current-driven magnetostatic effects. This work establishes a scalable and physically intuitive approach for tailoring magnetic domain configurations in microscale amorphous alloys, offering valuable insights for designing compact, highly sensitive MI sensors for flexible electronics, biomedical diagnostics, and intelligent sensing technologies.