Ultrafast Magnetization Manipulation Using Single Femtosecond Light and Hot-Electron Pulses

Abstract

Current-induced magnetization manipulation is a key issue for spintronic applications. This manipulation must be fast, deterministic, and nondestructive in order to function in device applications. Therefore, single- electronic-pulse-driven deterministic switching of the magnetization on the picosecond timescale represents a major step toward future developments of ultrafast spintronic systems. Here, the ultrafast magnetization dynamics in engineered Gd_x[FeCo]_1−x-based structures are studied to compare the effect of femtosecond laser and hot-electron pulses. It is demonstrated 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, it is shown that the limiting factor of such manipulation for perpendicular magnetized films arises from the formation of a multidomain state due to dipolar interactions. By performing time-resolved measurements under various magnetic fields, it is demonstrated that the same magnetization dynamics are 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 enhanced due to the ballistic transport of hot electrons before reaching the GdFeCo magnetic layer.

Deterministic switching of magnetization without any external magnetic field is demonstrated using single femtosecond hot-electron or laser pulses in an engineered Gd_xFeCo_1−x-based structure. It is found that a hot-electron pulse allows a reversed magnetic state within 40 ps in either Gd-rich or FeCo-rich alloys, similar to a femtosecond laser pulse. This study paves the way for ultrafast spintronics.

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