Meander-like CoP/Cu Bilayer Sensing Elements Based on the Giant Magnetoimpedance Effect

Meander-like sensors based on the giant magnetoimpedance (GMI) effect are excellent candidates for magnetic applications due to their low cost, tunable sensitivity, compactness, and room-temperature operation. The GMI effect is characterized by large variations in the electrical impedance of magnetic materials under low applied magnetic fields (H). In this work, CoP sensing element films, a ferromagnet with low coercivity and high magnetic permeability, were electrodeposited onto meander-like Cu structure patterned on fiberglass substrates using a printed circuit board assembly (PCBA) technique. Each meander has 12 arms, 0.2 mm wide and 5.0 mm long, with a 0.2 mm separation between them. The CoP films, with thicknesses of 4.5 µm, 10 µm, and 19 µm, exhibited a composition of Co (90.1%) and P (9.9%), as determined by energy-dispersive spectroscopy (EDS). Magnetic hysteresis curves showed that the CoP/Cu meander sensing elements have a well-defined easy axis in-plane along their larger dimension, with a coercive field of 8 Oe. The GMI was measured by using a Vector Network Analyzer for frequencies (f) up to 1.8 GHz and for H in the range ± 3.0 kOe. The thickest sample yielded a GMI of 55.13% for H = 58.8 Oe, for a current of 6.12 mA and f = 1.8 GHz, corresponding to an overall sensitivity of 0.4 Ω/Oe. These results present a viable alternative for developing GMI-based sensors through established, low-cost techniques like electrodeposition and PCBA.