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Investigation of bit patterned media, thermal flying height control sliders and heat assisted magnetic recording in hard disk drives

Abstract

Many advanced technologies in the field of magnetic disk recording are being studied in order to achieve areal densities in excess of 1.6 gigabits per square millimeter (1 terabits per square inch). Bit patterned media (BPM) is one of these promising technologies. By using disks with physically separated magnetic patterns instead of conventional continuous media, bit patterned media avoid magnetic interference between adjacent bits and improve the thermal stability of the media. Currently, thermal flying height control (TFC) sliders are commonly used to compensate thermal effects during reading and writing and to maintain a stable and ultra-low head/disk spacing during drive operation. Heat assisted magnetic recording (HAMR) has been introduced in order to address difficulties in writing of information on magnetic media with high coercivity. By using a laser beam to locally heat the media above its Curie temperature, the magnetic material momentarily reduces its coercivity and permits writing of information on the disk. However, the method raises concerns about the stability of the lubricants on the disk. In this dissertation, we focus on the investigation of the head/disk interface for bit patterned media, the design of thermal flying height control sliders, and the implementation of heat assisted magnetic recording. In particular, we use a finite-element-based air bearing simulator to study the steady-state flying characteristics of sliders flying over bit patterned media. This air bearing simulator is then combined with a thermo-mechanical model of a slider in order to analyze thermal flying height control sliders featuring dual heater/insulator elements. Next, a finite element model of a thermal flying height control slider with an integrated heat assisted magnetic recording optical system is developed to study the effect of heat dissipation along the laser delivery path on the performance of the HAMR-TFC slider. The design parameters of the dual thermal flying height control heaters are optimized in order to minimize the dependence of the head/disk spacing on laser induced thermal effects. Finally, experimental techniques are developed to investigate the photo-thermo stability and tribological properties of HAMR-type lubricants which are designed to be resistant to the high temperatures experienced under laser exposure

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