Interface Magnetization Switching and Demagnetization in \textit{Fe/Al} films and \textit{Fe/Pt} nanoparticles

We report on the reversal and demagnetization processes of the Fe interface layer magnetization in thin films and nanoparticles of \textit{Fe/Al} and \textit{Fe/Pt} by time-resolved magnetization-induced second-harmonic generation. The results are compared with those of the bulk magnetization as obtained from magneto-optic Kerr effect. We realize that switching and demagnetization characteristics are distinctly different between bulk and interface layers because of the interface-derived anisotropy and the dipole interactions. In particular, the surface and interface magnetism will dominate the behaviors of nanoscale structures.