Domain Structure and Magnetization Reversal in Multilayer Structures Consisting of Thin Permalloy Films Separated with Nonmagnetic Interlayers

Using numerical micromagnetic modeling, we have investigated the development of domain structure and magnetization reversal in multilayer thin-film structures. The permalloy (Ni80Fe20) magnetic layers had the inplane uniaxial and perpendicular magnetic anisotropy. We found that as the thickness of nonmagnetic interlayers decreases, the in-plane configuration of magnetic moments in the permalloy layers transforms from a single domain state to stripe domains, which is caused by the increase of magnetostatic interaction between layers. In structures with “thick” interlayers, even weak magnetostatic interaction enforces the neighboring single domain permalloy layers to have opposite orientations of magnetic moments. The saturation field of such samples increases linearly with the number of layers. By analyzing the dynamic characteristics of multilayers, we determined the optimum number of layers ensuring the maximum conversion efficiency of wideband microwave microstrip sensors of weak magnetic fields.