hesela.devThermal asperity
A thermal asperity is a transient magnetoresistive read-signal disturbance caused by frictional heating during contact with a disk asperity or particle.
The sensor's temperature-dependent resistance can add a nonmagnetic disturbance to the readback signal [1]. This names the thermal signal event, not the surface bump itself.
Non-contact baseline disturbance is different: changing head-disk clearance can change cooling of a biased sensor without frictional heating [2]. The CML follow-up models this with two-dimensional heat conduction and warns that neglected out-of-plane conduction may overestimate temperature [3].
The non-contact estimate on report 97016's printed page 14 compares about 0.008 ohm with a normal magnetic readback excursion of 0.5% of 30 ohms, or 0.15 ohm. This gives roughly 5% of that signal, not 5% of total sensor resistance. The abstract and conclusion instead give about 10%; no corrected value is asserted. This is not a contact-thermal-asperity amplitude [2].
Relations
Limitations
- These historical MR-head mechanisms do not provide a universal modern-drive amplitude, SMART diagnosis or fleet failure rate. [2, 3, 1]
Citations
- Klaassen and van Peppen: Electronic abatement of thermal interference in (G)MR head output signals (1997), IBM author record; DOI 10.1109/20.617425
- Zhang and Bogy: Variation of the Heat Flux between a Slider and the Air Bearing when the Slider Flies over an Asperity, CML report 97016, introduction and model
- Zhang and Bogy: Temperature Response of a MR Head When It Flies over an Asperity, CML report 98001, sections 1, 5.2 and 6
Further reading
Sources & caveats
- Source synthesis, not a new experiment. The CML model and discussion sections were checked beyond their abstracts; the IBM record supplies an author-hosted abstract, not full-text circuit verification.