Compositional Dependence of g-Factor and Damping Constant of GdFeCo Amorphous Alloy Films

Time-domain magnetization dynamics of sputtered GdFeCo (30 nm) amorphous alloy films was measured by pump-probe method using high-power ultra-short pulse fiber laser. The effectiveg-factorgeffand effective damping constantαeffof the GdFeCo films were estimated by using a numerical calculation of Landau–Lifshitz–Gilbert equation. The precessional frequency took a maximum near the magnetization compensation compositionCMof the GdFeCo, while the estimatedgeffandαeffincreased around the angular momentum compensation compositionCA. The compositional dependences ofgeffandαeffwere roughly described by a mean-field model. Thegeffandαeffwere also estimated from the ferromagnetic resonance (FMR) spectra, and the data from the FMR spectra agreed well with those from the pump-probe measurement except for the composition nearCM. The FMR method was unable to excite the magnetization nearCMbecause of the small net magnetization.