NiFe/INSULATOR/Cu COMPOSITE WIRES AND THEIR GIANT MAGNETO-IMPEDANCE EFFECTS

Abstract

In this work, two types of electrodeposited Ni–Fe /insulator/ Cu composite wires, namely Ni–Fe /seed layer/glass coated copper wire (Composite Wire A), and Ni–Fe /seed layer/sputtered SiO2/Cu (Composite Wire B), have been fabricated and their giant magneto-impedance effects have been investigated. With different implementations of the insulator layer, the magneto-impedance effect of Composite Wire A, whose insulator layer is cast from the melt Pyrex, is significantly higher than that of Composite Wire B with an insulator of sputtered SiO 2 layer. The profile of the insulator layer, as well as the thickness of magnetic layer and the diameter of the conductive core, greatly influences the interaction between the magnetic layer of Ni–Fe and the copper core, as shown in their giant magneto-impedance (GMI) effects. The maximum MI ratios obtained from Composite Wires A and B are 226% at 800 kHz when H ext = 0.87 Oe , and 95% at 1 MHz when H ext = 0 Oe , respectively. The Composite Wire A is a promising candidate for the sensing element of high sensitivity sensors to very weak magnetic field. For Composite Wire B, further improvement on its GMI effect and sensing performance requires optimization of its geometric parameters and the deposition conditions.