Influence of Thickness on Magnetic Properties of Electrolytic Ni-Fe Films Deposited on Cu Wires

The influence of film thickness on magnetic properties of Ni-Fe films electroplated under tensile stress on 50
$\mu{\rm m}$
Cu wires is investigated by means of hysteresis loops, FMR (ferromagnetic resonance) and MI (magnetoimpedance) measurements. With increasing thickness the coercive force and the remanence ratio decrease. The MI and network analyzer-FMR (NA-FMR) measurements indicate the presence of a strong uniaxial anisotropy along the wire axis in the thin films. With increasing film thickness the anisotropy gradually changes to the hard-wire-axis anisotropy. While the hard-axis anisotropy of thick films can be ascribed to the magnetoelastic coupling with the compressive back-stresses in the Ni-Fe layer, the easy-axis anisotropy of thin films is probably due to the surface anisotropy at the Ni-Fe/Cu interface.