  The speed of magnetization reversal is a key feature in magnetic data
storage. Magnetic fields from intense THz pulses have been recently shown to
induce small magnetization dynamics in Cobalt thin film on the sub-picosecond
time scale. Here, we show that at higher field intensities, the THz electric
field starts playing a role, strongly changing the dielectric properties of the
cobalt thin film. Both the electronic and magnetic responses are found to occur
simultaneously, with the electric field response persistent on a time scale
orders of magnitude longer than the THz stimulus
