Magnetization dynamics from an ab-intio perspective: from single atoms to skyrmions*

One of the major challenges in information technology is to find new paradigms to increase computing speed and storage capacity. Today, several high-potential future bits are heavily explored across several length scales: from e.g. single atoms to large magnetic objects such as skyrmions. This requires concomitantly careful investigations and understanding on the mechanisms permitting their stability, their detection and manipulation, which are highly dynamical in nature leading to formidable computational challenges because of the complex interactions of the magnetic bits with the surrounding degrees of freedom.

I will present an overview of our investigations for different atoms deposited on several substrates. Combining time-dependent density functional theory and many-body perturbation theory, we showed that current-driven spin-state manipulation in nano-devices leads to rich transport patterns with new many-body features, resulting from the interaction of the electrons and the spin-excitations detectable with state of the art inelastic scanning tunneling spectroscopy. The intricate interplay between the intra- and interatomic exchange interactions and the spin-orbit interaction dramatically modify the dynamical behaviour of the nanomagnets and the lifetime of the newly produced state. Furthermore, I will address zero-point spin-fluctuations leading to a collapse of the magnetic anisotropy energy barrier even at absolute zero temperature and I will provide practical guidelines for designing magnetically stable nanomagnets with minimal quantum fluctuations. Finally, utilizing a multi-scale modelling approach, I will discuss the dynamics of sub-5 nm skyrmions heavily affected by the presence of single atomic-defects, which can act as pinning or repulsive centers depending on their chemical nature.