Aug 29, 2002
Nanoscale patterns boost magnetic density
Increasing magnetic recording density has become an important goal for many in the hard-disk-drive industry. But recording on a continuous film at higher densities generally means decreasing the grain size, and that can cause the magnetization of the grains to become thermally unstable. Now, a team of scientists from IBM has developed a film-patterning technique that could overcome this issue and suit large-scale manufacturing.
"One solution that is being explored to get round the problem is to pre-pattern the magnetic media into isolated magnetic regions, so that each region acts as a single magnetic domain," Gary McClelland of IBM's Almaden Research Center, US, told nanotechweb.org. "To make this technology commercially viable, the magnetic bits must be patterned very cheaply, with a resolution that is 3 times as great as that currently achievable by optical lithography. We showed that these requirements can be met by imprinting the bit pattern using an inexpensive photocured resist material as a flexible stamp."
The IBM researchers created magnetic islands 55 nm in diameter over 3 cm-wide areas of substrate. To achieve this, they imprinted a flexible resist etch mask onto a silicon dioxide substrate, etched a pattern of pillars in the substrate, and then evaporated an 11 nm-thick magnetic cobalt-platinum multilayer film onto the pillars. "The substrate topography isolates the magnetic material on top of each pillar, creating single domains," said McClelland.
"By using a flexible stamp, we can accommodate the small but inevitable surface roughness and curvature present in glass disk substrates," he added. "The method may be the basis for large-scale manufacturing, because an essentially unlimited number of the flexible stamps can be fabricated from a single master template made by e-beam lithography. Each of the stamps may be able to make many hundreds of patterned disks."
The scientists reported their work in Applied Physics Letters. Now they plan to "imprint smaller magnetic islands, begin flying a recording slider/head on [their] patterned disk and characterize its magnetic writing and reading behaviour".
About the author
Liz Kalaugher is editor of nanotechweb.org.