Flying Characteristics on Discrete Track and Bit-Patterned Media With a Thermal Protrusion Slider

Abstract

Future disk drives may have discretized tracks or bit patterns for increased thermal stability and higher areal density. This affects the surface topography, resulting in different flying characteristics of the currently used air bearing slider. The actual flying height drop versus the pattern density and pattern depth has not been measured yet. However, it has been recently simulated. We have made flyable patterned disks with angular sections having various topographies. This allowed the measurement of flying height modulation and clearance drop within one revolution in different sections of the disks. Slider-to-disk clearance changes were measured using pulsed thermal protrusion. Furthermore, we investigated the slider dynamics and disk-lubricant changes during the transition from a flat zone to a patterned zone. This is of relevance since the servo sectors have different patterns compared to data zones on the disk leading to dynamic excitations and flying height modulation. These effects may still be detectable even after disk planarization since they are periodic and may excite the air bearing resonance. Based on our experimental observation, we have established an empirical equation that predicts slider clearance loss versus pattern density. The clearance change was measured when the slider air bearing was transitioning from a large scale pattern (in micrometers) to a small scale pattern (in nanometers), indicating increased lift with an increased number of walls/holes-even at a similar nominal pattern density. Functional drives were built that contained discrete track media with imprinted servo sectors.