Graphene overcoats for ultra-high storage density magnetic media

Hard disk drives (HDDs) are used as secondary storage in digital electronic devices owing to low cost and large data storage capacity. Due to the exponentially increasing amount of data, there is a need to increase areal storage densities beyond ~1 Tb/in2. This requires the thickness of carbon overcoats (COCs) to be <2 nm. However, friction, wear, corrosion, and thermal stability are critical concerns below 2 nm, limiting current technology, and restricting COC integration with heat assisted magnetic recording technology (HAMR). Here we show that graphene-based overcoats can overcome all these limitations, and achieve two-fold reduction in friction and provide better corrosion and wear resistance than state-of-the-art COCs, while withstanding HAMR conditions. Thus, we expect that graphene overcoats may enable the development of 4–10 Tb/in2 areal density HDDs when employing suitable recording technologies, such as HAMR and HAMR+bit patterned media

HDI Tribology Challenges and Strategies of Heat Assisted Magnetic Recording Drives

The key features for Heat Assisted Magnetic Recording (HAMR) head-disk interface (HDI) are higher temperature, rougher media grains and harder disk properties. As a result of these features, it is critical for HDI especially the head to remain wear resistance, contamination robustness and chemical stability as much as possible compared to the current Perpendicular Magnetic Recording (PMR) technology. This work summarizes new tribology challenges and strategies at the HDI arisen from the HAMR technology, in terms of disk carbon overcoats, lubricants, head overcoats and mechanical design.

Correlation of Disk Topography Waves With Nanometer Scale Lubricant Moguls

Magnetic recording disk carbon overcoats are lubricated with nanometer thick films of perfluoropolyether lubricant. It is well-known that lubricant thickness redistribution takes place due to air shear stress oscillation at air bearing resonant frequencies and also due to shear stress oscillation induced by disk topography waves on test tracks. We extended this work to demonstrate correlation between surface topography and lubricant redistribution on whole disk surfaces. Lubricant moguls are shown to form over regions of the disk surface which have topography waves that are half the slider length, and the lubricant thickness peak is out of phase down track from the topography peak height. There is a critical relative humidity above 20% beyond which moguls are readily formed by the slider flying at 10 nm without thermal fly height control. The significance of the lubricant redistribution for drive magnetic performance has long been the subject of debate. These results demonstrate that lubricant thickness redistribution on the order of atomic diameters can degrade magnetic performance, and that the surface topography waves alone can degrade areal density by as much as 2%.