Nutation Wave as a Platform for Ultrafast Spin Dynamics in Ferromagnets

Imam Makhfudz, Enrick Olive, Stam Nicolis

Published 2019-10-25Version 1

The inertia term becomes relevant for the magnetization dynamics of ferromagnets at short time scales and leads to nutation motion of the magnetization vector. In the simplest model, of a Heisenberg spin chain with isotropic spin-exchange interaction, the occurrence of a "nutation wave" is analytically demonstrated and numerically confirmed. The corresponding excitation spectrum describes relativistic massive particles. The single-particle excitation, the "nutaton", acts like the Higgs boson with respect to an emergent topological gauge field. This spin excitation would appear as a peak in the spectrum of the scattering structure factor from inelastic neutron scattering experiments. The high frequency and speed of the nutation wave can open new paths towards new ways of realizing ultrafast spin dynamics.