Magnetization Dynamics in FePt Nano-Granular with Thermal Heating Observed by All-Optical Pump-Probe Method

Heat assisted magnetic recording (HAMR) is used to switch the magnetization of FePt nano-granular film in hard-disk-drive. To understand the magnetization switching behavior, magnetic damping constant is used as an important material parameter. However, the observation of magnetization dynamics and evaluation of magnetic damping constant for FePt thin film is technically difficult because its precession frequency reaches several hundred GHz. All-optical pump-probe technique have been used to detect such high frequency magnetization dynamics. Here, fast magnetization dynamics in FePt thin films with thermal heating was investigated to clarify the temperature dependence of magnetic damping constant. The effective magnetic damping constant for the FePt nano-granular thin film exhibit minimum at 620 K, and its value was evaluated to 0.064.