Growth- and measurement-temperature dependence of Gilbert damping in Co₅₀Pt₅₀ films with perpendicular magnetic anisotropy

Gilbert damping characterizes the dissipation of magnetization dynamics and is crucial for controlling both magnetization switching and magnon propagation. This work systematically investigates the influences of substrate temperature (T_s = 25 −500 ℃) and measurement temperature (90 −295 K) on the static and dynamic magnetic properties of Co₅₀Pt₅₀ (CoPt) films grown on the MgO (111) substrate. When T_s exceeds 200 °C, the magnetic anisotropy transitions from in-plane to perpendicular, with the largest uniaxial anisotropy field occurring near 300 °C. The Gilbert damping exhibits a nonmonotonic dependence on T_s, arising from competition between intrinsic spin–orbit-coupling–related relaxation and extrinsic damping associated with increased surface roughness at high T_s. Temperature-dependent TR-MOKE measurements further reveal distinct behaviors: the RT-grown CoPt film with in-plane anisotropy shows a monotonic decrease in damping with increasing measurement temperature, consistent with conductivity-like intrinsic behavior. In contrast, the film grown at 500 °C with perpendicular anisotropy displays a pronounced damping peak near 150 K, followed by a reduction attributed to the suppression of two-magnon–scattering-driven extrinsic damping at low temperatures. These results deepen the understanding of damping mechanisms in magnetic systems with strong spin-orbit coupling and provide valuable guidance for designing low-temperature spintronic devices.