Dual stripe sensor on a picoslider for in-contact thermal asperity testing

The use of anisotropic magnetoresistive (MR) heads at low flying height has led to the phenomenon of thermal asperities, read signal spikes caused by thermal effects when a slider impacts disk asperities. This paper presents a proposal for a wide trackwidth thermal asperity test head with a dual stripe sensor on a picoslider. While it turns out that a single stripe is sufficient to detect thermal asperities, a dual stripe sensor has the added advantage of being capable of reading magnetic index marks on the disk. This allows one to trace an asperity location after the disk has left the test stand. A thermal asperity signal waveform typically starts out with an undershoot. This effect is caused by greatly enhanced sensor cooling due to a reduction of the head to disk clearance when approaching the thermal asperity.