Domain-wall motion induced by spin transfer torque delivered by helicity-dependent femtosecond laser

TL;DR

This paper demonstrates that combining femtosecond laser pulses with current pulses reduces the power needed to move magnetic domain walls in perpendicular anisotropy wires, with laser helicity influencing the displacement.

Contribution

It introduces a method to lower domain wall motion power threshold by using simultaneous laser and current pulses, highlighting the dominant role of spin transfer torque over spin orbit torque.

Findings

Domain wall displacement depends on laser helicity.

Spin transfer torque dominates over spin orbit torque in this setup.

The combined effect can be modeled with the Fatuzzo-Labrune model.

Abstract

In magnetic wires with perpendicular anisotropy, moving domain with only current or only circularly polarized light requires a high power. Here, we propose to reduce it by using both short current pulses and femtosecond laser pulses simultaneously. The wires were made out of perpendicularly magnetized film of Pt/Co/Ni/Co/Pt. The displacement of the domain wall is found to be dependent on the laser helicity. Based on a quantitative analysis of the current-induced domain wall motion, the spin orbit torque contribution can be neglected when compared to the spin transfer torque contribution. The effective field of the spin transfer torque is extracted from the pulsed field domain wall measurements. Finally, our result can be described using the Fatuzzo-Labrune model and considering the effective field due to the polarized laser beam, the effective field due to spin transfer torque, and the Gaussian temperature distribution of the laser spot.