Tailoring optical excitation to control magnetic skyrmion nucleation

In ferromagnetic multilayers, a single laser pulse with fluence above an optical nucleation threshold can create magnetic skyrmions, which are randomly distributed over the area of spot. However, in order to study dynamics skyrmions and for their application future data technology, controllable localization skyrmion sites is crucial. Here, it demonstrated that patterned reflective masks behind thin film be designed locally tailor excitation amplitudes reached, leading spatially controlled on nanometer scale. Using x-ray microscopy, influence nanopatterned back-side aluminum studied two sample geometries varying layer sequence substrate Co/Pt multilayer. Surprisingly, masks' effect suppressing or enhancing skymion reverses when changing this sequence. Moreover, near-field enhancements additionally affect spatial arrangement nucleated skyrmions. Simulations modulation excitation, following heat transfer across interfaces employed explain these observations. The results demonstrate reliable approach add nanometer-scale control optically induced magnetization processes ultrafast timescales.