Gilbert damping in perpendicularly magnetized Pt/Co/Pt films investigated by all-optical pump-probe technique

To investigate the correlation between perpendicular magnetic anisotropy and intrinsic Gilbert damping, time-resolved magneto-optical Kerr effect was measured in Pt/Co(d(Co))/Pt films. These films showed perpendicular magnetization at d(Co)=1.0 nm and a perpendicular magnetic anisotropy energy K(u)(eff) that was inversely proportional to d(Co). With an analysis based on the Landau-Lifshitz-Gilbert equation, the intrinsic Gilbert damping constant alpha was evaluated by parameter-fitting of frequency and lifetime expressions to experimental data of angular variations in spin precession frequency and life-times. The alpha values increased significantly with decreasing d(Co) but not inversely proportional to d(Co).