Figure 1: Temporal responses in the non-adiabatic regime.

(a) Free induction decay responses of the TR-MOKE experiment for applied magnetic fields of 100 mT (blue), 300 mT (Red), 500 mT (yellow) and 700 mT (green). Traces are shifted along the y axis for clarity. (b) Schematic of the experimental set-up. A femtosecond pulse laser is phase-locked to a microwave oscillator. External magnetic field is applied in the sample plane causing precessions about the x axis while the out-of-plane component of the magnetization, m_z, is detected in a polar-MOKE configuration. The magnetic film was patterned into a square island and the microwave signal was transmitted by a shorted Au microwire. β represents the angle of polarization rotation. (c–e) Temporal responses of the pump-probe FMR measurement at 10 GHz and H₀ values of 422 mT (c), 434 mT (d), and 443 mT (e) and microwave field amplitude of∼0.8 mT. The pump pulse arrives at t=0 ps. The resonance field at this frequency is μ₀H_res∼450 mT. Each trace is normalized to the peak value. Arrows indicate the envelope minimum. (f) Measured temporal responses at 10 GHz for a complete range of applied fields. Each trace is normalized individually to the peak value. The solid red lines were plotted using the Rabi formula. Also the second Rabi oscillation is readily seen (black dashed line). Inset illustrates the trajectory of the magnetization vector, M, on the sphere of constant saturated magnetization. 10 GHz magnetization precessions take place about the axis while the slow variations in the , or component of M obey Rabi’s formulae.