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IBM is working on an new type of memory that combines the pace and reliability of flash with the low cost and high capacity of hard drives.
In two papers published in Science, IBM fellow Stuart Parkin described the technology that he and a team of scientists are
working on, called 'racetrack' memory.
He believes the milestone could mean devices capable of storing far more data in the same amount of space than currently possible. Spin-offs include super-fast boot times, low cost and unprecedented stability and durability.
Called racetrack memory because data runs around a wire 'track', it could eventually lead to solid state devices capable of storing 500,000 songs or 3500 movies - about 100 times more than possible today - with far lower cost and significantly less power consumption.
Aside from being able to shoehorn massive amounts of data into these devices, IBM says they would be practically unbreakable, capable of running on a single battery for weeks at a time, and could last for decades.
"It has been an exciting adventure to have been involved with research into metal spintronics since its inception almost 20 years ago with our work on spin-valve structures," said Parkin.
"The combination of extraordinarily interesting physics and spintronic materials engineering, one atomic layer at a time, continues to be highly challenging and very rewarding. The promise of racetrack memory - for example, the ability to carry massive amounts of information in your pocket - could unleash creativity leading to devices and applications that nobody has imagined yet."
The two current storage mediums both have their shortfalls. Solid state flash memory is durable and can read data quickly but has a finite lifespan and is slow to write data. Hard disk drives, with a lot of moving parts have reliability issues.
Racetrack memory has no moving parts, using the 'spin' of an electron to store data, so can be rewritten almost infinitely without causing wear.
On the racetrack
Scientists have long explored the possibility of storing information in magnetic materials by using 'domain walls', the boundaries between magnetic regions in the material. The costly, complex and power-hungry process made the process incredibly difficult.
Dr. Parkin and his team describe how this long-standing obstacle can be overcome by taking advantage of the interaction of spin polarised current with magnetisation in the domain walls.
This results in a spin transfer torque on the domain wall, causing it to move.
The use of spin momentum transfer considerably simplifies the memory device since the current is passed directly across the domain wall without the need for any additional field generators.
The system magnetic domains to store information in columns of magnetic material (racetracks) arranged perpendicularly or horizontally on the surface of a silicon wafer.
Magnetic domain walls are then formed within the columns delineating regions magnetised in opposite directions (e.g. up or down) along a racetrack.
Each domain has a "head" (positive or north pole) and a "tail" (negative or south pole). Successive domain walls along the racetrack alternate between "head to head" and "tail to tail" configurations. The spacing between consecutive domain walls (that is, the bit length) is controlled by pinning sites fabricated along the racetrack.
In their paper, the scientists describe their use of horizontal permalloy nanowires to demonstrate the successive creation, motion and detection of domain walls by using sequences of properly timed nanosecond long spin-polarised current pulses. The cycle time for the writing and shifting of the domain walls is a few tens of nanoseconds.
These results illustrate the basic concept of a magnetic shift register relying on the phenomenon of spin momentum transfer to move series of closely spaced domain walls an entirely new take on the decades-old concept of storing information in movable domain walls.
Ultimately, the researchers expect the construction of a novel 3D racetrack memory device, moving away from two-dimensional arrays of transistors and magnetic bits.
Dr. Parkin's advances with racetrack memory build on his accomplishments in memory technologies including the spin valve, and Magnetic Tunnel Junctions (MTJs) and breakthroughs in magnetic RAM (MRAM).
Racetrack memory encompasses the most recent advances in this realm, the field of metal spintronics.
The spin-valve read head enabled a thousand-fold increase in the storage capacity of the hard disk drive in the past decade; the MTJ is in the process of supplanting the spin-valve because of its higher signal.
MTJs also form the basis of modern MRAM, in which the magnetic moment of one electrode is used to store a data bit. Whereas MRAM uses a single MTJ element to store and read one bit, and hard disk drives use a single spin-valve or MTJ sensing element to read the approximately 100 GB of data in a modern drive, racetrack memory uses one sensing device to read 10 to 100 bits.
- NZ HERALD STAFF
