Exploring the Fundamental Spatial Limits of Magnetic All-Optical Switching
Felix Steinbach, Unai Atxitia, Kelvin Yao, Martin Borchert, Dieter Engel, Filippo Bencivenga, Laura Foglia, Riccardo Mincigrucci, Emanuele Pedersoli, Dario De Angelis, Matteo Pancaldi, Danny Fainozzi, Jacopo Stefano Pelli Cresi, Ettore Paltanin, Flavio Capotondi, C. Masciovecchio, Stefan Eisebitt, Clemens von Korff Schmising
Abstract
All-optical switching (AOS) results in ultrafast and deterministic magnetization reversal upon single laser pulse excitation, potentially supporting faster and more energy-efficient data storage. To explore the fundamental limits of achievable bit densities in AOS, we have used soft X-ray transient grating spectroscopy to study the ultrafast magnetic response of a GdFe alloy after a spatially structured excitation with a periodicity of 17 nm. The ultrafast spatial evolution of the magnetization in combination with atomistic spin dynamics and microscopic temperature model calculations allows us to derive a detailed phase diagram of AOS as a function of both the absorbed energy density and the nanoscale excitation period. Our results suggest that the minimum size for AOS in GdFe alloys, induced by a nanoscale periodic excitation, is around 25 nm and that this limit is governed by ultrafast lateral electron diffusion and by the threshold for optical damage.