We investigated the three-dimensional dynamics of the magnetization vector launched by an intense infrared pulse of femtosecond duration in a thin Fe film. We demonstrate how a single experiment of time-resolved magneto-optical Kerr effect can provide quantitative information on the temporal evolution of the magnetization trajectory. Our approach allows us to follow the precessional motion of the magnetization and to retrieve the modulus and orientation of the magnetocrystalline anisotropy field as a function of time—and therefore of the local temperature—providing a direct experimental evidence of the phenomenological mechanism triggering
the magnetization precession
We have investigated the magneto-optical response of Fe epitaxial films by femtosecond pump-probe polarimetry in a broad probe spectral region (1.8-2.6 eV). From the extrapolated photoinduced variation of the conductivity tensor, spin and charge dynamics have been disentangled. In particular, the analysis of the off-diagonal tensor element rules out any appreciable modification of the electronic band structure upon laser excitation and suggests that ultrafast demagnetization is determined by collective excitations, i.e., spin fluctuations. Our experimental evidence provides significant insight into the microscopic mechanisms governing the complex spin dynamics of metals in the subpicosecond time scale.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.