Study of Slider Dynamics Over Very Smooth Magnetic Disks

Flying characteristics of 50 percent negative pressure sliders on aluminum, glass, and silicon disks with different surface characteristics are described. By using an AE (acoustic emission) and LDV (Laser Doppler Vibrometer) we were able to study the effect of surface roughness and disk materials on the dynamics of the slider. In the regime where the slider flies below the glide height (30 nm) and contact with the disk surface can occur, the AE signal consisted of low frequencies related to air bearing resonance (around 100 kHz), and high frequency related to slider body vibrations (735 kHz). Interestingly, in the high speed regime the AE signal contained low frequency signals. The signal increased as the fly height of the slider increased when flying on the smooth surfaces except on the silicon disk. LDV measurements revealed that the excitation from the silicon disk surface was smaller than on the aluminum disk or the glass disk by 10 dB, which contributed to suppress the vibration of the slider. For a given excitation from the disk, the surface roughness played a key role in determining the slider vibration. We also determined that a fly height fluctuation occurred due to the surface roughness, but the effect was found to be very small. The difference between the textured and smooth surface was from the damping effect on the slider vibration. The slider was made to collide with a protrusion fabricated on a disk surface to study the damping characteristics of the slider. The textured disk surface gave more damping than on the smooth disk surface by up to 20 percent.