Fig. 1. TR-MOKE response for 3 nm-thick Co₂FeAl film with an external field of 1.15 T and its best fitting (red solid line). The inset shows the schematic diagram of application of external magnetic field.

Fig. 2. For 3 nm-thick Co₂FeAl film, (a) TR-MOKE responses measured at different magnetic fields and their fittings (red solid lines), (b) the extracted oscillatory frequency as a function of external magnetic fields (the black squares represent the magnetization precession frequency and the red solid line is its best fitting; the colored dots represent the phonon modes whose frequencies do not depend on the magnetic fields). The inset in panel (b) shows the FFT spectrum of the TR-MOKE data measured at H = 1.6 T.

Fig. 3. The typical time-resolved reflection responses and their best fits (red solid line) for Co₂FeAl films with different thickness: (a) 3 nm-Co₂FeAl measured at probe wavelength of 800 nm, (b) 45 nm-Co₂FeAl measured at different probe wavelengths, (c) the extracted coherent acoustic phonon frequencies as a function of probe wavelength. The inset in panel (a) shows the schematic diagram of the experiment.

Fig. 4. For 3 nm-thick Co₂FeAl film: (a) the effective damping factors as a function of external magnetic fields, (b) the extracted magnetization relaxation time τ_M and acoustic phonon decay time τ_p.