Fig. 1: Spin valve structure and schematic representation of experimental scheme.

a Sample structure used to study the spin-polarized hot electron (SPHE) induced dynamics: SiN/Ta (5)/Cu (20)/Ta (5)/Fe₇₄Gd₂₆ (15)/Cu (10)/{Co (0.6)/Pt (1)}*3/Cu (60)/Pt (6). The thickness of each layer in the bracket is in nm. Here, the red pulse represents the IR laser (800 nm) of 60 fs duration acting as a pump, and the blue pulse represents the circularly polarized X-ray pulses of 100 fs duration as a probe. Both pulses are separated by 1°. The large arrow represents the direction of hot electrons flow, and inside, the short red arrow with a circle represents the non-polarized hot electrons. Cu (60) ensures the complete absorption of the IR pulse; therefore, the bottom Co/Pt layer is excited through HE pulses only. Consequently, those HE pulses generate spin-polarized current (SPHE) from Co/Pt. After crossing the spacer layer, the spin current interacts with the Fe₇₄Gd₂₆ layer, on which the response of SPHEs is recorded. b Parallel (P) and antiparallel (AP) experimental scheme: The Black, green, and blue arrows represent the Co, Fe, and Gd magnetization directions. AP and P define the relative orientations of the magnetization between Co and Fe in {Co (0.6)/Pt (1)}*3 and Fe₇₄Gd₂₆, respectively.