Heat Assisted Magnetic Recording Head-Disk Interface: Numerical Simulation of Air Bearing and Lubricant Mechanics

The hard drive industry widely views heat assisted magnetic recording (HAMR) as the technology to achieve 4 Tb/in2 and greater storage densities and recapture the aggressive storage density growth rates of years past so that hard disk drives are able to meet the world's exploding data storage demand. While traditional magnetic media is thermally unstable at room temperature for the small bit sizes needed for high density recording, the high coercivity HAMR magnetic media can safely store digital data at very small bit sizes of (25 nm)2. In order to write data, a near-field optical system confines electromagnetic energy below the dffraction limit to locally heat the HAMR recording bit to 400-500°C within a few nanoseconds. This adds new thermal complications to the already difficult mechanical and tribological design challenges for the head-disk interface (HDI) region. The reliability of hard drive read-write performance depends on the ability of the recording head slider, which contains the read and write elements, to stably fly in close proximity (< 5 nm) to the spinning recording disk. HAMR technology introduces heat-dissipating components and rapid thermal uctuations to the HDI system not seen in traditional hard drives. Numerical simulations provide insightful information into the performance of HDI components that are difficult or impossible to attain experimentally.;This dissertation focuses on numerically simulating the mechanics of two components of the HDI under HAMR conditions: (1) the air bearing pressurized air flow dragged in between the rapidly spinning disk and the slider that supports the ying slider to maintain a < 5 nm minimum spacing above the disk and (2) the 1--2-nm-thick polymer lubricant that coats the disk to protect it against intermittent contact with the slider. Both are modeled using lubrication theory that is modified for gas rarefaction or thin-film polymer effects in order to provide useful system-level predictions.;In this work, the fully generalized molecular gas lubrication equation that allows for nonisothermal conditions is the basis for a simulation tool used to numerically study the effects of heat dissipation by inefficient near-field optics system components on the air bearing performance. The iterative HAMR static solver solves the coupled problem of air bearing pressure generation and slider thermal deformation, linked by the heat transfer coefficient and pressure profile at the slider's air bearing surface (ABS). Static simulations are conducted for a simple HAMR slider in which the heat dissipating components are a thermal ying height control (TFC) heater, the near-field transducer (NFT), and laser diode. The NFT induces an additional 1--2 nm of localized protrusion compared to traditional TFC sliders, and it has the highest temperature of 175--300°C for the conditions tested. The waveguide dissipates heat away from the NFT and lowers the ABS maximum temperature, leading to a smoother NFT protrusion. Thermal creep, a rareified gas flow driven by temperature gradients on the boundary, causes additional ying height drop of 0.05--0.15 nm for sliders with minimum ying heights below 2 nm. The efficiency of the read/write transducer and NFT are extremely sensitive to ying height, so even these differences of 0.1 nm will be significant in 4 Tb/in2 HAMR systems in which the minimum ying height will only be 1 nm.