Picosecond pulsed-field probes of magnetic systems (invited)

Time-resolved methods using picosecond scale transient magnetic fields have been developed for investigations of ultrafast magnetic phenomena in a broad variety of systems. When combined with synchronous magneto-optic detection, the approach yields stroboscopic observations of magnetic dynamics with a time resolution of order 1 ps, and a corresponding spatial resolution down to the diffraction limit of optics. Results are presented from experiments on europium chalcogenide films at low temperatures. A continuum of behavior from paramagnetic relaxation to ferromagnetic resonance is observed. Electron-beam deposited EuS films are found to have surprisingly fast spin-lattice relaxation rates, of order (100 ps)-1, and the influence of spin-orbit interactions on the spin dynamics is studied through rare-earth alloying. Results are presented from experiments utilizing the magneto-optic sampling method for direct time-resolved screening measurements of normal and superconducting metal films.