High-Temperature Ferromagnetic Resonance in FePt Thin Films

Understanding of damping processes in ferromagnetic thin films at temperatures (T) near the Curie temperature (T_c) has significant implications for heat-assisted magnetic recording and magnetic sensors operating at elevated temperatures. Recent ferromagnetic resonance (FMR) studies [PR Applied 10, 054046 (2018)] using out-of-plane fields showed that there are two major relaxation processes in granular L1₀-odered FePt thin films at 10-45 K below T_c: two-magnon scattering and spin-flip magnon-electron scattering; with a decrease in T, the FMR linewidth increases due to the enhancement of the two-magnon scattering. This presentation reports high-T FMR studies on continuous FePt thin films with cubic structures, rather than L1₀ structures. The films are 6-nm thick and have T_c≈680 K; the FMR measurements were performed over 300-620 K in out-of-plane fields. As opposed to the L1₀ FePt films, the cubic FePt films show an FMR linewidth that decreases with a decrease in T. This T dependence suggests that the spin-flip magnon-electron scattering is dominant over the two-magnon scattering; the two-magnon scattering is weak because it is expected to be absent in continuous films under out-of-plane fields.