A study of the non-uniform effect on the shape anisotropy in patterned NiFe films of ferromagnetic resonance

A systematic ferromagnetic resonance (FMR) study shows that an in-plane magnetic anisotropy in the patterned submicron rectangular permalloy elements is mainly determined by the element geometry. As the aspect ratio increases, the in-plane shape anisotropy increases, but the contribution from the non-uniform demagnetizing effect decreases. An expression is proposed to represent the in-plane shape anisotropy due to the non-uniform demagnetizing effect. When the magnetic field is applied near the film normal direction, a set of evenly spaced peaks appears on the low-field side of the main FMR peak. The multiple peaks are considered as spin-wave resonance spectra of non-uniformly magnetized elements.