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 μm Cu wires is in- vestigated 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.