Ultrafast Magnetization Manipulation Using Single Femtosecond Light and Hot-Electron Pulse*

Current induced magnetization manipulation is a key issue for spintronic applications. This manipulation must be fast, deterministic and non-destructive in order to function in device applications. Therefore, single electric pulse driven deterministic switching of the magnetization at the picosecond timescale represents a major step towards the future developments of ultrafast spintronic systems. Here we have studied the ultrafast magnetization dynamics in engineered Gd_x[FeCo]_1-x based structures to compare the effect of femtosecond laser and hot-electron pulses. We demonstrate that a single femtosecond hot-electron pulse causes deterministic magnetization reversal in either Gd-rich and FeCo-rich alloys similarly to a femtosecond laser pulse. In addition, we show that the limiting factor of such manipulation for perpendicular magnetized films arises from formation of a multi-domain state due to dipolar interaction. By performing time resolved measurements under various magnetic fields, we demonstrate that the same magnetization dynamics is observed for both light and hot-electron excitation, and that the full magnetization reversal takes place within 40 ps. The efficiency of the ultrafast current induced magnetization manipulation is optimized thanks to the ballistic transport of hot-electrons before reaching the GdFeCo magnetic layer.