Off-Transition Noise Characterization During Head Thermal Protrusion

This paper characterizes the read-back off-transition noise (OTN) in spectral, spatial, and time domains during the thermal protrusion of a magnetic head. In perpendicular recording, the OTN is typically lower than the background noise, and shows bathtub-like cross-track profile. The spatial and spectral characteristics of the read-back OTN make it sensitive to the head positing change in cross-track, down-tack, and vertical directions. In contrast to the conventional on-transition signal reading, the OTN monitoring reverses the usage of signal and noise and lowers the requirement on signal quality. Monitoring OTN during head´s thermal control can detect air bearing´s stability, head´s fly-ability, and head-lube/disk contact without Fourier transform (FT) related techniques. A single-track and single read-frequency head-lube/disk contact detection method with high simplicity, high sensitivity, and high repeatability is introduced.