GRAPHENE

Graphene protective coating could signal ‘ultra-high storage density’ media, say

Analysis scientists writing in Nature Communications have mentioned that switching to graphene protecting coating on disk drive patters and browse/write heads opens the way in which to 4–10 Tb/in2 areal density HDDs utilizing HAMR and HAMR+bit patterned media.

Trying on the present 1 1Tb/in2 areal density utilized in 18TB, 9-platter drives with a 2TB/platter capability, you can extrapolate the appliance of the tech as ushering in an period of, for instance, 180TB 9-platter drives.

As the dimensions of the bit space on a disk platter floor decreases, the sign displaying its magnetic pole course decreases in depth: making it tougher to detect. The sign amplitude might be elevated if the learn/write heads fly nearer to the disk platter’s recording medium. Each the learn/write head and the platter recording medium are protected by so-called carbon overcoat (COC) safety layers. Making the head-platter recording medium hole smaller means having thinner safety layers. However there shall be issues with friction, put on, corrosion, and thermal stability if COC thickness goes beneath 2nm with HAMR recording expertise.

The group, which included boffins from the Nationwide College of Singapore, the Argonne Nationwide Laboratory within the US, the CSIR-Superior Supplies and Processes Analysis Institute in India, and Cambridge and Exter within the UK, wrote that present COC thickness is 3nm and that’s used to make disk drives with a 1Tb/in2 areal density (AD). Their paper features a graphic displaying a disk drive platter and browse/write head hole:

a) Schematic cross-section of a tough disk drive with magnetic medium, disk overcoat, lubricant, fly top, head overcoat, head. The pinnacle-medium spacing and fly top/clearance are indicated by arrows. The slider containing the learn/write head and the top overcoat are proven as nicely. For 1 Tb/in2, the head-media spacing is ~8.9–6.5 nm, primarily based on the sum of overcoat thickness (2.5–2 nm), lubricant thickness (1.2–1 nm), contact down top (2–1 nm), fly clearance (1.2–1 nm) and head overcoat thickness (2–1.5 nm). A1TiC stands for Aluminium-Titanium-Carbide.

The paper’s authors famous: “A COC thickness <1 nm can be required for ~10 Tb/in2. Nonetheless, present COCs lose most of their interesting properties, similar to anti-friction, put on resistance, Younger’s Modulus, and corrosion safety, when their thickness is under 2–3 nm.” [Young’s modulus is a measure of a material’s tensile stiffness.]

On high of this HAMR (Warmth-Assisted Magnetic Recording) requires laser-produced warmth to be utilized to the bit areas to allow bit values to be written. COCs endure degradation when their thickness goes beneath 4nm in HAMR circumstances and the authors wrote “the overcoats for HAMR require thermal stability at the least as much as ~700–800 Ok to keep away from degradation over time.”

Graphene, mentioned to be 200 instances stronger than metal, could possibly be used as a substitute of peculiar carbon because the protecting overcoat. It’s another type of carbon with a single layer of carbon atoms organized in a 2-dimensional hexagonal lattice.

They researchers investigated the usage of 1–4 layers of chemical vapour deposition (CVD) grown graphene (1–4LG) with HAMR expertise. They discovered very excessive wear-resistance, thermal stability, good corrosion resistance and anti-friction properties. The paper acknowledged: “Thermal stability assessments affirm that 1LG on FePt (Iron-Platinum) can face up to HAMR-like circumstances, with out degradation. Graphene’s superior efficiency and its thinness can allow the event of ultra-high-density magnetic knowledge storage applied sciences.” 

These embrace “bit patterned media (BPM), the place the magnetic storage layer is patterned into an array of pillars, every representing a single bit.” In truth: “The mixture of 1LG + HAMR + BPM could improve AD > 10 Tb/in2.”

We’ve tabulated the results on disk drive capability of accelerating areal density by extrapolating from at the moment’s 18TB, 9-platter drives utilizing 1 Tb/in2 aerial density:

Seagate CTO John Morris advised an funding analyst briefing in February that 2.6Tb/in2 is “able to supporting 40TB in our nine-platter nearline drive.” A straight extrapolation would offer a 46.8TB drive. He mentioned “the feasibility for attaining a product cargo of fifty terabytes by 2026.”

A ten Tb/in2 aerial density implies {that a} 180TB, 9-platter disk drive might (in principle) be produced. That is past the HDD capability projections talked about in public by HDD makers. For instance, Morris advised the funding analysts: ”We’ve a path to 10 terabytes per disk [platter] by 2030, that means a 90TB, 9-platter drive.”

That means a 5Tb/in2 aerial density. The analysis scientists’ paper hypothesises that double that density is in the end achievable by altering from carbon overcoats to graphene ones. 

This assumes that HAMR and BPM expertise might be developed appropriately, after all.

Boot notice

Full textual content of the article is offered right here: Dwivedi, N., Ott, A.Ok., Sasikumar, Ok. et al. Graphene overcoats for ultra-high storage density magnetic media. Nat Commun 12, 2854 (2021).

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