Unlocking of remanent magnetization of pole heads by "Rumble Strips"

Pole heads used for perpendicular recording can remain magnetized after the write current has been switched off. In this locked state, the remaining magnetization leads to erasure of data previously written on the disk (erase-after-write). We report experimental data which show that the length of the erasure is the range of several microseconds up to a few milliseconds. Moreover, it is observed that the locked remanent magnetization state of the head can be destroyed by magnetization patterns that already exist on the disk at the time of writing. It is concluded that magnetization patterns creating rotating fields are most efficient in destroying these remanent states.