The computer hard discs of the future will have a higher data-storage capacity through the clever use of heating or microwave energy. Researchers at Toshiba have discovered a stepping-stone solution that may help pave the way to those next-generation discs.
A hard disc consists of spinning platters covered in microscopic magnetic particles known as grains. The magnetic orientation of a small cluster of grains determines whether a single bit – the smallest unit of computational information – is a 0 or a 1.
These grain clusters have become smaller and smaller as manufacturers have sought higher data density. But if they are too small, then very little energy is needed to change their magnetic orientation, leaving bits susceptible to accidental flipping from 0 to 1, or vice versa, and damaging the data on the disc.
To fix this problem, manufacturers have used materials with stronger magnetic properties for the grains, meaning they are more likely to hold on to their orientation without flipping. But this leads to a new problem: the components in the hard disc that encode data by flipping the magnetic grains, known as the read/write head, are themselves becoming smaller to increase data density, and these components risk becoming too small and underpowered to flip the strongly magnetic grains.
In the next generation of hard discs, heat or microwaves will help give the read/write head the extra energy required to flip the magnetic grains, but this will require redesigning the spinning platters using new materials.
Now Hirofumi Suto and his colleagues at Toshiba have discovered a technology for the short term that uses microwaves with existing platter materials.
While working with experimental microwave-assisted switching (MAS) devices, they identified an approach called flux control that improves the ability to flip grains, albeit to a limited extent, by amplifying the magnetic field from the read/write head.
They realised that this approach works without having to create special materials for the platters, which is essential in a full MAS system. Using this approach, the Toshiba team created a commercial hard disc that is now on sale in capacities up to 18 terabytes, which use nine stacked platters in a helium-filled enclosure.
No one at Toshiba was made available to discuss the new work before publication of this story.
Siva Sivaram at rival hard disc maker Western Digital says the technology is a stepping stone, but that engineering problems are now forcing a total rethink of traditional designs.
“Now it’s getting tougher and tougher, you have to think of this whole thing holistically. Heat is the way forward for everybody for the long term. In the middle of the decade, 2024, 2026, you’re going to have heat. But it adds a lot of cost and complexity and reliability issues,” he says.
Journal reference: Journal of Applied Physics, DOI: 10.1063/5.0041561