  We demonstrate a quasi ballistic switching of the magnetization in a
microscopic mag-neto resistive memory cell. By means of time resolved magneto
transport we follow the large angle precession of the free layer magnetization
of a spin valve cell upon applica-tion of transverse magnetic field pulses.
Stopping the field pulse after a 180 degree precession rotation leads to
magnetization reversal with reversal times as short as 165 ps. This switching
mode represents the fundamental ultra fast limit of field induced magnetization
reversal.
