Boffins join nanodots for storage breakthrough

A nanodot drive would have at least 100 times the capacity of today's devices

Magnetic particles just a few billionths of a metre across could hold the key to next-generation data storage drives with "at least 100 times the capacity" of conventional devices.

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated so-called 'nanodot' arrays that respond to magnetic fields with record levels of uniformity.

According to the scientists, the work enhances the prospects for commercially viable nanodot drives with at least 100 times the capacity of today's hard disk drives.

The researchers explained that nanodots have north and south poles like tiny bar magnets and switch back and forth (or between 0 and 1) in response to a strong magnetic field.

Generally, the smaller the dot, the stronger the field required to induce the switch. But until now the researchers have been unable to understand and control the switching.

The NIST team has succeeded in working with nanodots as small as 50nm wide. The key was to first lay down a tantalum "seed layer" just a few nanometres thick when making a multilayer film of alternating layers of cobalt and palladium on a silicon wafer. The seed layer can alter the strain, orientation or texture of the film.

By making and comparing different types of multilayer stacks, the researchers were able to isolate the effects of different seed layers on switching behaviour.

They were also able to eliminate factors previously suspected to be critical, such as lithographic variations, nanodot shape or crystal grain boundaries.

Nanodots are one of two major approaches being pursued around the world as possible means of boosting the density of magnetic data storage. The other involves using a laser to heat and switch individual bits.

The ultimate solution may be a combination of the two approaches, because he at reduces the strength of the magnetic field needed to switch nanodots, according to Justin Shaw, lead author of the new paper, Origins of Switching Field Distributions in Perpendicular Magnetic Nanodot Arrays, which appeared in the latest edition of the Journal of Applied Physics.

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