Head-disk dynamics in the flying, near contact, and contact regimes

To achieve an areal density approaching 50 Gb/in.(2) for the magnetic stora ge of data in hard disk drives requires reduced mechanical and magnetic spa cing. Off-track jitter caused by airflow or contact can cause track misregi stration on the order of 20-70 nm which may be excessive for adequate servo performance. The magnetic signal can be used to identify both the vertical sparing modulation due to the air bearing modes and off-track jitter due t o suspension modes with nanometer resolution. We find that the off-track ji tter in the flying regime is driven by airflow and is a strong function of the disk velocity and the suspension type. In the contact regime, the verti cal spacing modulation and off-track jitter increase due to contact. Using a laser Doppler vibrometer we identified the tending contribution to the of f-track jitter to be primarily the first torsional mode (TI) and to a lesse r extent the first bending mode (B1) of the suspension.