The optimization of the high frequency giant magnetoimpedance (GMI) effect and its magnetic field sensitivity in melt-extracted Co_69.25Fe_4.25Si₁₃B_12.5Nb₁ amorphous microwires was systematically studied through a multi-step Joule annealing (MSA) technique. The surface morphology, microstructure, surface magnetic property, and radio frequency GMI response of the Co-rich microwires were explored using techniques like microscopy, magneto-optical Kerr effect (MOKE) magnetometry, and the magnetic field dependence of the wire's radio frequency impedance (GMI). The multi-step Joule annealing protocol begins with an initial dc current amplitude (i_dc) of 20 mA that was stepped up by 20 mA every 10 min to a maximum amplitude of 300 mA. Radio frequency GMI measurements at 20 MHz demonstrated a remarkable improvement of the GMI ratio and field sensitivity to 760% (1.75 times of that of the as-prepared wire) and 925%/Oe (more than 17.92 times of that of the as-prepared wire), respectively, after the MSA protocol with a maximum current amplitude of 100 mA. Microscopy and MOKE suggest that the MSA technique can enhance the microstructure and surface magnetic domain structure of the Co-rich magnetic microwire, which would give rise to an improved GMI ratio. The high GMI sensitivity at small magnetic fields renders these MSA-treated Co-rich microwires highly promising materials for biomedical devices that sense and monitor small, biological magnetic fields.

通过多步焦耳退火 (MSA) 技术系统地研究了熔体提取的 Co _69.25 Fe _4.25 Si ₁₃ B _12.5 Nb ₁非晶微线的高频巨磁阻抗 (GMI) 效应及其磁场敏感性的优化。使用显微镜、磁光克尔效应 (MOKE) 磁力测定法和金属丝射频阻抗的磁场依赖性等技术探索了富钴微丝的表面形态、微观结构、表面磁性和射频 GMI 响应。 GMI）。多步焦耳退火协议从初始直流电流幅度 ( i _dc) 的 20 mA，每 10 分钟增加 20 mA，最大振幅为 300 mA。20 MHz 的射频 GMI 测量表明，GMI 比和场灵敏度显着提高至 760%（所制备导线的 1.75 倍）和 925%/Oe（所制备导线的 17.92 倍以上）线），分别在最大电流幅度为 100 mA 的 MSA 协议之后。显微镜和 MOKE 表明 MSA 技术可以增强富钴磁性微线的微观结构和表面磁畴结构，从而提高 GMI 比。在小磁场下的高 GMI 灵敏度使这些经过 MSA 处理的富钴微线成为用于感应和监测小生物磁场的生物医学设备的非常有前途的材料。