ABSTRACT
This chapter is dedicated to ab initio model to describe optical, ultrafast manipulation of magnetic clusters. After the discovery of laser-induced demagnetization the optical control of the magnetic state of both extended and finite materials has become an increasing field of research. The investigations mainly follow two paths. The first one is to try and understand the microscopic processes behind this exciting phenomenon while the other one aim at using it to coherently manipulate magnetic materials and, ultimately, design spintronic applications. Here, after a short historic review we will develop a first-principles model, which can explain ultrafast spin-switching on single magnetic centers. Then we will extend the system to include more magnetic centers. Doing so will allow, beside spin flip, also for spin transfer and thus will enable us to implement magnetic logic. As side considerations, we will discuss the effects of phonons, as an additional degree of freedom also connected to temperature, and of a metallic substrate, since they both can affect the optical selection rules in the clusters. We will close the chapter with a short assessment of the importance of our theoretical findings.
