Coupling of microwave magnetic dynamics in thin ferromagnetic films to stripline transducers in the geometry of the broadband stripline ferromagnetic resonance

摘要

We constructed a quasi-analytical self-consistent model of thestripline-based broadband ferromagnetic resonance (FMR) measurements offerromagnetic films. Exchange-free description of magnetization dynamics in thefilms allowed us to obtain simple analytical expressions. They enable quick andefficient numerical simulations of the dynamics. With this model we studied thecontribution of radiation losses to the ferromagnetic resonance linewidth, asmeasured with the stripline FMR. We found that for films with largeconductivity of metals the radiation losses are significantly smaller than formagneto-insulating films. Excitation of microwave eddy currents in thesematerials contributes to the total microwave impedance of the system. Thisleads to impedance mismatch with the film environment resulting in decouplingof the film from the environment and, ultimately, to smaller radiation losses.We also show that the radiation losses drop with an increase in the striplinewidth and when the sample is lifted up from the stripline surface. Hence, inorder to eliminate this measurement artifact one needs to use wide striplinesand introduce a spacer between the film and the sample surface. The radiationlosses contribution is larger for thicker films.