At long last, engineers at Florida International University have found a way of breaking the 2D limitation of magnetic hard drive storage. By moving to three dimensions, the researchers have massively increased areal density, with the possibility of 100-terabyte (and larger) hard drives now firmly on the horizon.

While we’ve covered a lot of magnetic storage breakthroughs, they have all been fundamentally 2D in their implementation, and thus are ultimately restricted by superparamagnetic limits (magnetic bits can only be so small, before neighboring bits/changes in temperature can randomly alter the magnetism). Heat-assisted magnetic recording (HAMR), for example, can allow for magnetic grains that are just a few nanometers across and areal densities in the terabits-per-square-inch domain — but even then, we’re still looking at a hard cap of around 60 terabytes per hard drive.

To move beyond the limits imposed by superparamagnetism, the only solution is move beyond simple 2D improvements — making magnetic grains smaller — and instead move into the third dimension.

At Florida International University, the researchers have created a new hard drive platter that allows for the writing and reading of 3D magnetic data. In essence, instead of having just one magnetic layer, the new platter has three magnetic layers, with isolation (insulation) layers sandwiched in between. On a conventional hard drive platter, a magnetic site stores just a single bit — here, a triple stack of magnetic layers, each magnetic site can store up to eight bits of data (north/north/north, south/south/south, N/N/S, N/S/S, etc.)

To read data, a weakly magnetic head is used to measure the vector sum of the three magnetic fields. To write data, each layer of the recording medium has slightly different properties, so that they can only be written by a specific type and strength of magnetic field, which is output by a special recording head.

For now, FIU’s new magnetic recording medium is an in-the-lab tech demo. Where conventional hard drive platters are mass-produced using a simple process (magnetron sputtering), FIU’s platter is more like a small disc of silicon that goes through dozens of painstaking processes, including e-beam lithographic patterning. This isn’t to say that multilayer 3D (ML-3D) recording won’t become a reality, but alternatives such as HAMR are much closer to commercial adoption. That ML-3D might be used to create 100-terabyte (or larger) hard drives in the future, though, is still exciting news — and, interestingly, perhaps the technology that will finally kill off the magnetic tape, which is still hanging in there as the preferred bulk offline storage medium.

Research paper: doi:10.1371/journal.pone.0040134 – “Multilevel-3D Bit Patterned Magnetic Media with 8 Signal Levels Per Nanocolumn” [Open-access]