A Tiny Trampoline To Gauge Magnetism
EXOTIC METAL ALLOYS and other new materials could be the keys to powerful new computer chips and other electronic devices. But it helps if scientists can first determine the materials' magnetic properties. One way is to expose a sample to a massive magnetic force 1 million times that of the earth's magnetic field. Scientists create this force with a pulse of electricity that lasts one-hundredth of a second. There's just one problem: Measurements are difficult because the field disappears so quickly.
Physicist David J. Bishop and his colleagues at Lucent Technologies Inc.'s Bell Laboratories have an ingenious solution for split-second magnetic measurement. Following the principle that "fleas are faster than elephants," as Bishop puts it, his team designed a tiny trampoline just 300 microns across--about three times wider than a human hair (picture). Anchored by four springs, the trampoline's net is stretched just above a fixed electrical plate.
In the center of the trampoline, the researchers put a one-microgram speck of material. When they flick the switch on the magnet, the sample is pulled toward the plate. The amount of movement indicates the sample's degree of magnetization, Bishop says. "The trampoline is so small that it can move in the same time scale as the magnetic force." In April, Bishop proved the device works by testing the magnetization of a superconductor with properties that are already known. The results are described in the May 1 issue of Science.