Thermomechanical Contact Between Magnetic Recording Head and Disk Defect Accounting for Heat Partition Factor

Abstract

The formation of defects on a magnetic recording disk is one of the critical issues in the reliability of a hard disk drive. When a magnetic recording head comes into contact with a disk defect, the resulting surface damage can cause significant degradation on read/write performance. Considering the carbon atoms in diamond like carbon (DLC) coating can experience phase change and oxidation under high temperature (i.e., mechanical softening process due to the thermal stability), the frictional heat generated by the sliding contact between a head slider and a disk defect can lead to severe damage on the head DLC film. In addition to the mechanical degradation of the head DLC film, the magnetic properties of underlying read/write elements and shield materials can also be deteriorated due to the mechanical stress and high temperature rise. In this paper, the thermomechanical contact between a head slider and a disk defect was systematically examined through analytical modeling and simulations. For the three different disk defects (i.e., Al2O3, SiO2, and AlTiC), the temperature rise and distribution on the contact area were determined from a theory of contact mechanics and heat transfer with the modified Francis heat partition factor. To obtain more physical insight into the thermomechanical head disk contact, parametric study was performed using a modified control parameter (ψ*), which was made of material properties of a disk defect and system operating conditions. According to the simulation results, it was observed that Al2O3 showed the worst thermomechanical contact performance among the three defects as it generated the highest flash temperature of 439.0°C on the head DLC film. The increased surface temperature was high enough to degrade the head DLC film as well as the underlying magnetic materials. Moreover, it was found that the surface temperature rise on a head slider was proportional to the values of ψ*.