Effect of Magnetic Coating Layer Thickness on the Magnetic Properties of Electrodeposited NiFe/Cu Composite Wires

One critical factor affecting the performance of nanocrystalline electrodeposited Ni₈₀Fe₂₀/Cu composite wires as the sensing elements of magnetoimpedance (MI) effect sensors or orthogonal fluxgate sensors is the thickness of the magnetic coating layer. In this study, the effect of the deposited layer thickness on the material composition, grain size, uniformity, coercivity, and the wire´s MI effect has been investigated. Electrodeposited Ni₈₀Fe₂₀/Cu wire samples of 20 mum in diameter coated with a layer of Ni₈₀Fe₂₀ of thicknesses ranging from 1-12 mum were developed and characterized. The results showed that: 1) the Fe concentration of deposited Ni-Fe decreased with increasing thickness, 2) the deposited materials uniformity increased with increasing thickness, and 3) the deposited material grain size increased with increasing thickness. As a combined effect of the three, the deposited materials coercivity seemed to remain unchanged as the thickness varied. However, the MI effect of the composite wire varied with the thickness, which could mainly be due to the geometrical effect caused by the coating thickness variation