Demagnetizing factors in patterned CoNiFe films with rectangular elements

CoNiFe patterned films with rectangular elements, all 600 nm wide but of different lengths, were fabricated and investigated by ferromagnetic resonance experiment and micromagnetic simulation. An in-plane magnetic uniaxial anisotropy was exhibited, and its value increases with an increase in the aspect ratio of the elements, which was fitted by the model, including a quasi-ellipsoid demagnetizing field and a non-uniform demagnetizing field. The relative importance of the non-uniform demagnetizing field decreased from 0.26 to 0.16 with an increase in the length-width aspect ratio of the patterned element from 1.5 to 10. The demagnetizing factors in the three principal axes were determined from the experimental data of ferromagnetic resonance, which agreed reasonably well with the values calculated by micromagnetic simulation. The calculation also indicated that the interaction between elements could be neglected when the edge to edge spacing between neighboring elements was larger than 3 μ in our patterned films.