Non-equillibrium ultrafast optical excitation as a stimulus for ultra-small field-free magnetic skyrmions in ferrimagnetic GdFeCo

TL;DR

This paper demonstrates the ultrafast, field-free creation and control of ultra-small magnetic skyrmions in GdFeCo using femtosecond laser pulses, advancing skyrmion-based memory technology.

Contribution

It reveals the mechanisms of skyrmion nucleation via ultrafast laser heating and shows how laser parameters and magnetic fields can control skyrmion properties.

Findings

Skyrmions can be nucleated within picoseconds using femtosecond laser pulses.

Magnon localization and coalescence stabilize skyrmions at zero magnetic field.

Laser pulse width, fluence, and external magnetic fields influence skyrmion size and number.

Abstract

Generating and manipulating magnetic skyrmions at ultrafast time scales is essential for future skyrmionbased racetrack memory and logic gate applications. Using the atomistic spin dynamics simulations, we demonstrate the nucleation of ultra-small field-free magnetic skyrmions in amorphous GdFeCo at picosecond timescales by femtosecond laser heating. The ultrafast nature of laser heating and subsequent cooling from a high-temperature state is crucial for forming magnetic skyrmion. The magnon localization and magnon coalescence are the key driving mechanisms responsible for stabilizing the magnetic skyrmions at zero field conditions. The polarization and, hence, the topological charge can be switched by exploiting the all-optical switching observed in GdFeCo. The skyrmion sizes and numbers can be controlled by varying pulse width and fluence of incident laser pulses. Applying an external magnetic field provides an additional degree of freedom to tune the skyrmion radius during the ultrafast optical creation of magnetic skyrmions. Our results provide a detailed understanding of the ultrafast creation of magnetic skyrmions using femtosecond laser pulses, a vital step in advancing next-generation skyrmion-based memory technologies.