Time resolved Kerr microscopy: Magnetization dynamics in thin film write heads

We have used a scanning Kerr microscope set-up with picosecond time resolut ion and submicron spatial resolution to directly measure the flux response in magnetic recording heads. The data rate limiting factor of a write head, which is the flux rise time at the gap, has been measured for different ge ometries and head materials in polar Kerr mode. Flux propagation in the yok e, which is governed by a combination of wall displacement and magnetizatio n rotation, has been studied by one dimensional and two dimensional time re sponse measurements utilizing the longitudinal Kerr effect. The local flux time response in the head was correlated to the respective micromagnetic st ructure as determined by static wide-field Kerr imaging. In addition to the intrinsic magnetic properties we have also studied the flux time response by looking at the system properties of the head/write-electronic and, by us ing a voltage source for excitation, information about classical eddy-curre nt effects for different pole geometries have been derived. Further, non-st ationary effects in the flux reversal process are shown to produce non-line arities in the response at the write gap which are contributing to non-line ar transition shift in the write process.