  Current induced magnetization manipulation is a key issue for spintronic
application. Therefore, deterministic switching of the magnetization at the
picoseconds timescale with a single electronic pulse represents a major step
towards the future developments of ultrafast spintronic. Here, we have studied
the ultrafast magnetization dynamics in engineered Gdx[FeCo]1-x based structure
to compare the effect of femtosecond laser and hot-electrons pulses. We
demonstrate that a single femtosecond hot-electrons pulse allows a
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 the
multi-domain formation due to dipolar interaction. By performing time resolved
measurements under various field, we demonstrate that the same magnetization
dynamics is observed for both light and hot-electrons excitation and that the
full magnetization reversal take place within 5 ps. The energy efficiency of
the ultra-fast current induced magnetization manipulation is optimized thanks
to the ballistic transport of hot-electrons before reaching the GdFeCo magnetic
layer.
