Precise frequency tuning of giant magnetoimpedance in CoSiB thin films via competitive stress relaxation and induced anisotropy

The complex distribution of internal stress and magnetic anisotropy in magnetron-sputtered amorphous films often renders their high-frequency Giant Magnetoimpedance (GMI) response unpredictable, limiting their utility in customized frequency applications. This study elucidates the competition mechanism between “thermally activated stress relief” and “field-induced anisotropy” during magnetic field annealing, offering an effective approach for tuning the GMI frequency response. Using 300 nm CoSiB amorphous films, we demonstrate two distinct regimes: (1) A Low-Temperature Region (∼300 °C) governed by stress relief, where thermal activation enhances permeability, driving a significant “Red-shift” of the peak frequency from 60 MHz to 30 MHz and yielding a peak GMI ratio of 4.1% with a maximum sensitivity of 0.22%/Oe. (2) A High-Temperature Region (>400 °C) governed by incipient crystallization, where magnetic hardening drives a blue-shift of the characteristic response toward 100 MHz. Furthermore, we observe a non-monotonic field dependence, with 30 Oe giving the most favorable response among the tested annealing fields. A qualitative/semi-quantitative analysis based on anisotropy-related magnetic dynamics is used to interpret these frequency shifts, providing physical insight into the regulation of the operating frequency window in single-layer CoSiB thin films.