Early stage of high speed switching in magnetic thin films

The early stage of high speed switching can be studied with a sufficient time resolution by measuring the amount of the irreversibly reversed magnetization caused by short and giant pulse fields (0.5 ∼ 10 ns, 20 ∼ 50 Oe) as a function of the pulse duration. The experiment has been done by means of the Kerr magnetooptic measurement of the reversed magnetization after an irreversible magnetization reversal is caused by the pulse field in the presence of a crossed steady hard direction field. From the disturbing experiments of this magnetization reversal process, it is concluded that, because of the giant amplitude of the pulse field, the rotation angles of the magnetization come to have a widely spread spatial distribution during the short pulse duration. Therefore, a part of the magnetization which rotates beyond the hard axis at the end of the pulse field is irreversibly reversed completely in about 30 ns and after then remains without drastic changes. This gives the basis of the present new method to study the early stage of the switching. By means of this method it is found that the variation in the reversed magnetization at the early stage is not monotonic but oscillatory.