Wei H. Yao

Head-disc dynamics of low resonance laser textures-a spectrogram analysis

Spectrogram analysis provides a systematic way to study the head-disc interface dynamics and demonstrates how the frequency spectrum varies during the head take-off or landing. The regular pattern laser texture has strong input excitations, which includes not only the fundamental frequency of bump pitch density but also the higher order harmonics. When the excitation frequencies intercept the system resonance frequencies, such as the slider/sensor body natural frequencies, the sensor output is amplified, which causes a false reading in the glide testing and glide avalanche measurement. Spiral-line laser texture solves the problem of resonance by completely removing the source of excitation.

Dynamics of glide head in the proximity contact regime

The intrinsic glide capability of a magnetic disk is typically assessed by the glide avalanche test with an acoustic emission (AE) or a piezoelectric transducer (PZT) sensor and is found to be a function of asperity height distribution. In this work, the dynamics of a glide head in the near contact regime is investigated. Both the laser Doppler vibrometer (LDV) and PZT techniques are used to monitor the head dynamics during the touchdown process on disks with different roughness. It is shown that the glide avalanche readings can be affected by the collapse of the air bearing. The comparison of the PZT and LDV responses during the glide avalanche process indicates a general agreement between these two methods.