Figure 3. Time-resolved precession of magnetisation of Ni.

(a), Illustration of the experimental configuration for the measurement of TR-XMCD. The sample is placed face-down on a CPW and incident circularly polarised x-rays pass through a hole in the signal line. The magnetisation of the stack about H_bias is driven by the RF field, H_RF. The cone angle of precession is exaggerated for clarity; the typical magnitude of precession is ~ 1°. (b), TR-XMCD data for Ni₈₁Fe₁₉ continuously driven at 4 GHz for the Co₅₀Fe₅₀(30)/Bi₂Se₃(8)/Ni₈₁Fe₁₉(30) sample (thicknesses in nm). Varying static bias field indicated by colour of lines, offset for clarity, showing increase in amplitude and phase shift across resonance at 14 mT. Solid lines are sine curve fits to the data.