Lateral and longitudinal finite size effects in NA-FMR measurements

The dynamic susceptibility of Permalloy films was measured using network analyzer ferromagnetic resonance, in order to study the broadband behavior of the damping parameter. The susceptibility is extracted from the transmission coefficient of a microwave propagating through a waveguide loaded by the magnetic sample. At low frequencies, the period of the microwave is much greater than the propagation time through the waveguide. The impedance due to the magnetic film is localized, and can be treated by simple signal theory. However, at high frequencies, the extracted signal can be significantly distorted by propagation effects. Here we present calculations taking into account the effect of the propagation, and show how to correct experimental data.