Head and Media Instantaneous Contact Friction Measurement and Glide Test

We have developed an in situ head disk friction measurement system using a laser Doppler vibrometer (LDV). With the high stiffness of the system and the high sampling rate of the LDV, the temporal resolution of the measurement is improved by 40 compared with the conventional strain gage apparatus. We estimate the instantaneous head disk contact friction to be as much as 8 of what would be otherwise measured with the conventional method. We present for the first time a clear evidence of head disk contact adhesion with the fast setup. Simultaneous piezo transducer (PZT) glide signal and friction measurement of the slider asperity contact show strong correlation between the two. Comparison of energy demonstrates that the mechanism of the glide test is a slider scratching event by the asperity, rather than the so called “collision” between the asperity and the head. The PZT signal comes from the friction-induced slider vibration after contact with the asperity.