Magnetic nutation: Transient separation of magnetization from its angular momentum

Abstract

Using a TR-MOKE experiment and atomistic spin dynamics simulations, the authors show here that a sudden, incoherent, ``kick'' to the spin system of a ferromagnet not only triggers the well-known precession (GHz range), but also, on top, a faster nutation (sub-THz range). The separation of magnetization from angular momentum leading to nutation is an inherent phenomenon occurring during the relaxation of a nonequilibrium excitation of a magnetic system using ultrashort optical pulses. The study allows us to integrate different processes, ranging from demagnetization via nutation to precession in a single experiment.