Broadband Mag-Noise of Patterned Permalloy Thin Films

A Y-factor noise figure (NF) measurement method is developed to characterize high-frequency mag-noise of a 550 nm wide Permalloy strip array under different dc bias currents. The noise voltage density is obtained. The proposed lumped element transmission line model describes noise properties of the patterned Py array well. Measurement data show that rapid ferromagnetic resonance frequencies (FMR) shift induced by dc bias current is related to the excess magnetization fluctuation thermally created by the combined dc current Joule heating effects and orthogonal Oersted fields.