Multiplex magnetic field annealing evoked remarkable GMI improvement in co-based amorphous wires

We have proposed a series of novel tailoring techniques for integrating conventional vacuum annealing (CVA) and the specific (e.g. transverse- and rotated-) magnetic field annealing (as denoted by TMFA and RMFA respectively), and systematically investigated the impacts of them on the giant magnetoimpedance (GMI) properties and domain microstructure of Co-based amorphous wires. Experimental results indicated that a multiplex MFA treatment i.e, two-step CVA annealing under a rotated magnetic field of 4000Oe, can realize remarkable enhancement of GMI in comparison with the as-prepared, CVA-treated and MFA-treated wires. The GMI ratio increased firstly and then tended to be stable with increasing frequency, moreover, both permeability and GMI ratio decreased with the increase of DC magnetic field. At 13 MHz, the maximum GMI ratio [ΔZ/Zmax]max and field response sensitivity ξmax of RMFA-ed wires increased to 398.39% and 21.84%/Oe, respectively, which is 2.41 times and 3.17 times than those of 165.18% and 6.88%/Oe for the as-prepared wires. Essentially, the physical process of RMFA action is mainly described as the multi-angle induced magnetic anisotropy and atomic reordering dynamic process due to the co-action of rotatory variation magnetic field energy and thermal activation. Meanwhile, the GMI behavior of TMFA evolving from single peak (SP) to double peaks (DPs) is attributed to the increase of magnetic domain driving force (namely domain wall movement increment) and uni-directional inducing magnetic anisotropy at relatively high frequency, which modified the GMI ratio and field sensitivity to 334.61% and 33.51%/Oe, respectively. Therefore, it can be concluded that both RMFA & TMFA would be used to explore microwires with enhanced GMI property for high-performance sensor applications.