Starting with the famous discovery of Einstein and De Haas, it has been common knowledge that magnetic moment and angular momentum are physical properties which are fundamentally connected. As a consequence, electrodynamics is coupled to quantum mechanics and the transfer and control of angular momentum is a key aspect for the understanding of magnetic materials and the development of future spintronic applications. As a further consequence, precession dominates magnetization dynamics in analogy to the mechanical motion of a spinning top.

 

When a ferromagnetic film is excited by strong, ultrashort laser pulses, it can lose its magnetic order almost completely on femtosecond time scales. Only recently we could demonstrate that, on the same time scale, the spin angular momentum is transferred to the lattice via the ultrafast creation of chiral phonons that absorb the angular momentum of the spin system. In this talk I will focus on the dynamics of spin angular momentum and on the development of a framework for the simulation of coupled spin-lattice dynamics. Furthermore, I will show how magnetic inertia can separate the dynamics of the magnetization from its angular momentum, an effect that in mechanics is known as nutation.