What do digital cameras, computer game devices, laptop computers, and portable music players have in common? They all use magnetic disk drives that rely on magnetostrictive read heads. "The read head is like a jet flying at supersonic speeds a meter above a pasture and counting the grass blades pointing in two different directions," says Oak Ridge National Laboratory (ORNL) researcher Bill Butler. He says electronic devices relying on magnetostrictive read heads are about to hit a wall as their disk drives get smaller and smaller. The reader, which works with the read head, is a device consisting of nickel iron and cobalt layers separated by copper spacers only a few nanometers thick. As disk drives downsize, the materials from which they are made approach their fundamental performance limits. "At just a few nanometers, you reach the superparamagnetic limit," says ORNL physicist Malcolm Stocks. "At that point, the magnetic properties are no longer stable." ORNL and the Department of Energy's Brookhaven National Laboratory are collaborating for the purpose of overcoming the limits. The government researchers are working with private companies and examining the structure of magnetic materials at the atomic scale so that designers of magnetic media may continue shrinking the size of disk drives. ORNL is using an IBM supercomputer for modeling the interfaces between silicon and silicon dioxide as well as helping design structures for smaller read heads. Using computer simulation, ORNL researchers obtained insight into anti-ferromagnetism in iron manganese. The new structures may contain iron, manganese, and rare-earth thin films that offer higher magnetic saturation. For more information, call (865) 574-5163, visit www.ornl.gov or write to ORNL, Box 2008, Oak Ridge, TN 37831.
With a better understanding of materials’ response to load and temperature, researchers could potentially use the knowledge to improve design. The research could even help geologists studying plate tectonics.
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