A Dynamic Scratch Test to Study Read/Write Head Degradation Due to Head-Disk Interactions

A dynamic scratch test is described to study read/write head degradation due to head-disk interactions. The test involves flying magnetic recording heads over custom-made asperities on the surface of a hard disk. Degradation of the read sensor amplitude, asymmetry, magnetic stability, pinned-layer flip, overwrite, and resistance were observed. The changes are attributed to stress induced magnetic anisotropy and/or scratching/smearing damage. Testing comparison of a giant magnetoresistive (GMR) and a tunneling magnetoresistive (TMR) head design showed that the TMR design was more susceptible to abrupt resistance decrease and amplitude loss, consistent with scratching/smearing damage at the air bearing surface.