Second harmonic generation in thin permalloy film

Abstract

Second harmonic generation versus strength and direction of the applied static magnetic field was measured for a thin permalloy (Ni80Fe20) film in a microstrip line at a driving frequency of 1 GHz and maximum input power of ∼110 mW. The measurements revealed two peaks in the double frequency signal—in the low static field (∼10 Oe) and the high one (∼45 Oe). To explain these findings, a macrospin model of a thin magnetic film with in-plane uniaxial magnetic anisotropy was considered. A perturbation expansion of the Landau–Lifshitz–Gilbert equation provided an explanation of the experimental data. The analysis of the model revealed that the low-field peak was caused by the longitudinal second-order magnetization component and the high-field peak by the transversal one. It was also shown that the uniaxial magnetic anisotropy of the film and the dependence of the magnetic damping parameter on the applied field play an important role in the process of the second harmonic generation. The results obtained give insights into some peculiarities of the nonlinear magnetization dynamics that are important in the development of magnetic film-based devices in the field of microwave signal processing and manipulation.