Scientists have produced a novel type of nanoparticle that they say could make it possible to dramatically increase magnetic-based data storage on future generations of computer hard drives. The researchers at Brown University and Sandia National Laboratories have announced new ways to create iron-platinum nanorods and nanowires. The materials can potentially provide a way to make far denser magnetic media. In doing so, the new materials could make possible devices that do not have the limits that many scientist anticipate conventional magnetic storage technologies will soon encounter.
Magnetic media store information in tiny sectors of magnetically aligned particles created from alloys of cobalt, platinum, and chrome. To fit more information in a smaller space, manufacturers need to make those sectors even smaller. The problem is that further shrinking the particles of these traditional materials causes them to lose their magnetic orientation at room temperature, corrupting any data they may store. Some experts believe that conventional magnetic storage techniques will reach their limit by about 2010.
To continue to increase storage capacity, making room for more songs, film clips, and multimedia files, researchers are searching for new materials. Iron-platinum is particularly interesting since it’s known to maintain its magnetism at the nanoscale. Nanorods and nanowires of the material also have the potential to align themselves in a controlled way, with each particle pointing in the same direction. If iron-platinum particles could be made to the desired specifications, and could be used in magnetic media, “that would push storage densities up by a factor of 10,” says Seth Darling, a researcher in magnetic materials at Argonne National Laboratories.
In May, a research group at Sandia National Laboratories was the first to report creating iron-platinum nanowires and nanorods. Getting the particles to properly align remains a problem, however. “The perfect circumstance would be if the rods aligned in one direction, in bundles,” says Hongyou Fan, a researcher at Sandia. “That’s what people dream of achieving.” If the particles did all point in one direction, researchers could use them to make the thin magnetic films required for use in magnetic media. More recently, a group at Brown University announced that it was able to synthesize iron-platinum nanorods and nanowires with increased control of the particles’ composition and shape. Shouheng Sun, a researcher at Brown, says that the improved control of shape and composition should lead to the production of particles that self-assemble in the desired array.
Sun’s group controls the shape and composition of the particles by varying the concentrations of surfactant, which affects surface tension, and solvent in the solution. The more surfactant the researchers use, the lower the surface tension, and the longer the wire they are able to produce. The researchers were able to form rods and wires with lengths ranging from 20 to 200 nanometers, with iron concentrations ranging from 45 to 55 percent. They hope to make particles shaped less like wires and more like bricks, which should be easier for engineers to use. Sun says that the particles his team produced align well but need further refinement to self-assemble in a fully parallel pattern.
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