Angular dependence of ferromagnetic resonance in Tb-doped Ni80Fe20 thin films

The mechanisms of angular dependence of ferromagnetic resonance (FMR) linewidth of dilute Tb doping in Ni80Fe20 thin films are investigated by experimental approach and the theoretical fitting by considering the contributions from intrinsic spin-orbit coupling, two-magnon scattering and inhomogeneous broadening. It is shown that the damping coefficient α, by intrinsic contribution extracted from FMR linewidth, is increased by more than 50 times as the Tb concentration increases to 8.4%, indicating that the spin-orbit coupling of this system increases with the introduction of Tb impurities. The magnetic anisotropy constants K1 and K2 are obtained and show an increasing trend from negative to positive, which implies that the Tb dopants could enhance the perpendicular anisotropy.