Phys. Rev. Lett. 110, 177205 (2013)

Magnetic skyrmions are topologically protected spin nanostructures that could be used to create novel magnetic information storage devices. To stabilize the structures, applied magnetic fields are required, but this limits their potential applications. Marco Finazzi and colleagues have now shown that skyrmion-like magnetic configurations can be generated in a thin ferromagnetic film by using single ultrafast optical laser pulses.

The researchers — who are based at the Politecnico di Milano, Radboud University Nijmegen, Nihon University and the University of Tokyo — generate single skyrmions in 20-nm-thick TbFeCo films using single laser pulses with a width of 150 fs and a wavelength of 800 nm. The magnetic nanostructures are observed by Faraday rotation, which maps the out-of-plane magnetization component. The lateral dimensions of the structures are in the range of a few hundred nanometres and can be tuned by changing the laser fluence. Higher laser fluences result in larger and more complex structures, such as annular magnetization configurations, which can be thought of as an anti-skyrmion nested in a skyrmion.

The presence of a finite uniaxial anisotropy in the films is sufficient to stabilize the structures, even in the absence of an external magnetic field