Optimized GMI Effect in Electrodeposited CoP/Cu Composite Wires

Influences of deposition time and electrolytic current density on the giant magnetoimpedance (GMI) effect of electrodeposited CoP/Cu composite wires were systematically investigated. The CoP magnetic layer was electrodeposited onto the Cu wire of 50 mm diameter. The thickness of CoP magnetic layer was controllably varied either by changing deposition time between t ¼ 2 and 10 min with a �xed electrolytic current density or by changing electrolytic current density between j ¼ 130 and 900 mA/cm2 at a given deposition time. Accordingly, the largest GMI effect was achieved in the wire sample with t ¼ 6 min and j ¼ 639 mA/cm2. At the measured frequency of 10.7 MHz, the GMI ratio and its �eld sensitivity reached the highest values of 534% and 21%/Oe, which is promising for high performance GMI sensor applications. It was proposed that the changes of deposition time and electrolytic current density caused variations in the domain structure of the CoP magnetic layer and hence the GMI behavior.