Thermal Protrusion-Induced Air Bearing Slider Instability at Disk Proximity and Light Contact

Nanoscale analysis characterized by microscopy with atomic resolution demand that the targeted surface remains nearly static. Therefore, the interaction between two fast moving surfaces requires a unique methodology to capture its dynamics when contacts are of nominal area on the order of 100 μm2 but only a few angstroms in depth. We present a contact study of the head-disk interface in hard disk drives, which consists of a disk surface coated with a molecularly thin perfluoropolyether lubricant and a slider surface moving slightly separated from it with a relative velocity of 20 m/s and with 10 nm spacing. By investigating the slider dynamics and lubricant topography in-situ, we disclose that high-speed contact initiates when the slider shears the top surface of the lubricant. Such contact can pile up molecules a few angstroms high as “moguls” or annihilate existing ones through a 5–10 Å interference. The transitional spacing regime of mogul evolution is defined as “quasi-contact,” and it is the initial contact in the fast sliding interface.

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Surface evolution of perfluoropolyether film at high speed quasi-contact conditions

Chen

Peng

Bogy

2016

Applied Physics Letters

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Investigation of heat transfer across a nanoscale air gap between a flying head and a rotating disk

Sakhalkar

Cheng

Ghafari

et al. 2020

Journal of Applied Physics

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Understanding nanoscale heat transfer at the head–disk interface (HDI) is necessary for thermal management of hard disk drives (HDDs), especially for heat-assisted magnetic recording and microwave-assisted magnetic recording. To accurately model the head temperature profile in HDDs, it is imperative to employ a spacing-dependent heat transfer coefficient due to the combined effects of pressurized air conduction and wave-based phonon conduction. Moreover, while flying at near-contact, the fly height and heat transfer are affected by adhesion/contact forces in the HDI. In this study, we develop a numerical model to predict the temperature profile and the fly height for a flying slider over a rotating disk. We compare our simulations with touchdown experiments performed with a flying Thermal Fly-Height Control (TFC) slider with a near-surface Embedded Contact Sensor (ECS), which helps us to detect the temperature change. We incorporate the effects of disk temperature rise, adhesion/contact forces, air and phonon conduction heat transfer, and friction heating in our model. As the head approaches the disk with increasing TFC power, enhanced nanoscale heat transfer leads to a drop in the ECS temperature change vs TFC power curve. We find that the exclusion of the disk temperature rise causes the simulation to overestimate the ECS cooling drop. The incorporation of adhesion force results in a steeper ECS cooling drop. The addition of phonon conduction in the model causes a larger ECS cooling drop. The simulation with friction heating predicts a larger ECS temperature slope beyond contact. The simulation with these features agrees with the experiment.

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Experimental and Simulation Study of Thermal Protrusion-Induced Head-Disk Contact Instabilities in Hard Disk Drives

2014

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Thermal Protrusion-Induced Air Bearing Slider Instability at Disk Proximity and Light Contact

Cited by 8 publications

References 17 publications

Surface evolution of perfluoropolyether film at high speed quasi-contact conditions

Surface evolution of perfluoropolyether film at high speed quasi-contact conditions

Investigation of heat transfer across a nanoscale air gap between a flying head and a rotating disk

Experimental and Simulation Study of Thermal Protrusion-Induced Head-Disk Contact Instabilities in Hard Disk Drives

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