Fig. 1. Configuration of the sample illumination with the pump and probe laser pulses. H is the external magnetic field. Before optical excitation, magnetization M is directed along H. A circularly polarized pump beam induces the magnetization dynamics, resulting in precession along a trajectory that is depicted by the green dashed line.

Fig. 2. (a) Scheme of the experiment with the variation of the pump beam position with ϕ changing from −π/2 up to π/2. (b) Normalized time-resolved change of the Faraday rotation indicating the magnetization precession excited by laser pulses in different external magnetic fields from 15 to 850 Oe. Inset: dependence of the precession frequency on the external magnetic field.

Fig. 3. (a) Normalized time-resolved change of the Faraday rotation indicating magnetization precession excited by pump beams of different azimuth angles. The pump beam azimuth angle varies from ϕ=−90  deg to ϕ=90  deg. Inset: zoom for easier tracking of the phase change. The black line is a guide for the eye demonstrating the A peak position change. All curves have offsets for clarity of representation. (b) Dependence of the phase angle on the sine of the pump azimuth angle. The angle of pump incidence is 17 deg. The external magnetic field is 850 Oe.