Extremely high frequency pulse magnetic resonance by picosecond magneto-optic sampling

An exceptionally broadband method for pulse magnetic resonance detection is described which enables measurements over a broad range of applied magnetic fields and affords excellent coupling to microscopic specimens. Employing a picosecond magneto-optic sampling technique with high temporal and spatial resolution, the precessing magnetization of a spin system is directly observed as a function of time following a photoconductively triggered spin tipping pulse. Free induction decays from 200 MHz to 200 GHz have been measured using a single device, for which the frequency limit in principle is of order 1 THz. Examples are presented for ferromagnetic resonance in yttrium iron garnet films at room temperature.