Magnetic properties of permalloy films with different thicknesses deposited onto obliquely sputtered Cu underlayers

In this work, the influence of obliquely sputtered Cu underlayer of 10 nm on the magnetic properties of normally sputtered Permalloy thin films with different thicknesses from 10 nm to 150 nm has been investigated. It has been found that the samples with the Permalloy layer thickness ranging from 10 nm to 70 nm exhibit a good in-plane uniaxial magnetic anisotropy, and the increase of the film thickness leads to a decrease of the anisotropy field and the natural resonance frequency. The critical Permalloy layer thickness for stripe domain initiation of these films is about 80 nm, which is thinner than that of obliquely sputtered Permalloy thin films without an underlayer. The characteristic shapes of hysteresis loops which can be called "transcritical" are observed above the critical thickness. The condition and mechanism of appearing stripe domain structure were discussed and it has been found that the frequency response of permeability of the anisotropic films shows the characteristics of multi-peak resonance. (C) 2014 Elsevier B.V. All rights reserved.