Figure 6: Dynamics of coupled photo-electron spin density and DW magnetization.

(a) Simulated time evolution of photo-electron spin density s at the centre of the DW generated by a 150 fs long LP indicated as a red arrow. Inset: the x, y, z components of s versus time t showing the fast precession around the exchange field of magnetization m. The red arrow in the inset indicates the LP. (b) The components of m and |m| versus t at a fixed position corresponding to the initial DW centre m^C. At t=0, m^C is oriented along the y direction at the centre of the Bloch-like DW. Note that m^C has been normalized by its modulus before the LP is applied. The graph shows a fast initial excitation due to the LP and a damped fast jiggling during the recombination time of the photo-electrons. During this short time, angular momentum is transferred from s to m^C causing a deformation of the DW. Note, that during the oSTT, the magnitude of |m^C| increases due to the interaction between the non-zero y component of the precessing spin density and the magnetization at the DW centre oriented initially also along y. (c) Time evolution of the DW deformation Δm along the DW width. The three plots show the time evolution of the deviation from the undisturbed DW profile in the rest frame of the domain wall with zero at the DW centre after the pulse was applied. The slowly relaxing DW deformation causes the DW motion. (d) The DW position as a function of time for the first three σ⁺-polarized LPs (a pulse occurs every 12.5 ns). In a–d, τ_rec=30 ps and R=1.2 × 10³⁹ m⁻³ s⁻¹.