All-optical control of ferromagnetic thin films and nanostructures: Competition between polarized light and applied magnetic field

The interplay of light and magnetism has been a topic of interest since the original observations of Faraday and Kerr where magnetic materials affect the light polarization. While these effects have historically been exploited to use light as a probe of magnetic materials there is increasing research on using polarized light to alter or manipulate magnetism. For instance deterministic magnetic switching without any applied magnetic fields using laser pulses of the circular polarized light has been observed for specific ferrimagnetic materials [1,2]. Very recently, we demonstrated, optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films (fig.1) being explored for ultra-high-density magnetic recording [3,4]. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed. These results challenge the current theoretical understanding and will have a major impact on data memory and storage industries via the integration of optical control of ferromagnetic bits. In this presentation we will study in detail the combine effect of applied magnetic field and polarized light. Depending on the light polarization and the applied field direction the two effect can add or cancel each other. The influence of both the helicity and the applied on domain structure is studied for different [Co/Pt] multilayers.