Magnetic softness of permalloy granular films produced by co-evaporation

In this study, magnetic softness of permalloy granular films produced by co-evaporation is investigated. Py (Ni₈₀Fe₂₀) is used as ferromagnetic source and one of MgF₂, SrF₂, and CaF₂ as matrix source. Resistivity is found to be about the same for all matrices and it extends to 10⁵ μΩcm. Above this limit, the films tend to exhibit superparamagnetic behavior locally and a hard-to-saturate curve is superimposed in their magnetization curves. As far as the ferromagnetic metal is Py, the anisotropy field Hk is about 50 Oe and this is common for all matrices. Perpendicular anisotropy is exhibited by a few series of samples such as Py-CaF₂ and Py-MgF₂. Therefore, by co-evaporation, magnetic softness, high resistivity and well defined frequency profiles are available in the as-made state for a variety of matrices with Py as a ferromagnetic component.