Tunable Linear Dependence of Giant Magnetoimpedance Response of Microwires Annealed under Fluid Oil for Sensor Applications

Abstract

Herein, fluid oil joule annealing modulation (FOJA) for improving the giant magnetoimpedance (GMI) property of CoFe‐based microwires with the microstructure is adopted, and magnetic domain structure is systematically investigated. Compared with general joule annealing (JA) method, a much larger DC current can be used. The maximum GMI value is 440.8% in the 250 mA FOJA‐treated sample and the maximum monotonically increasing magnetic field is 12 Oe in 400 mA FOJA‐treated sample. In the 100–400 mA FOJA‐treated samples, there is a nearly linear increase and decrease relationship between GMI and the magnetic field. In addition, the FOJA method can control the radial stress release and helical magnetic domains of the microwire by changing the Joule heat transfer and the circumferential magnetic field and then tune the GMI performance of the microwires. The remarkable features, including a continuous and clear linear‐sensitive response field Hex of 0–95 Oe, quick response sensitivity, large GMI ratio, and excellent tunability, make the FOJA‐tailored microwires promising candidate material for miniaturized GMI sensors.