MAGNETIC SWITCHING IN COBALT FILMS BY ADSORPTION OF COPPER

MAGNETIC storage of information requires the ability to manipulate the magnetization of thin films with high sensitivity and spatial resolut ion. Non-magnetic overlayers are known to affect the characteristics o f magnetic films: for example, the direction of magnetization of cobal t and iron films can be altered by deposition of a monolayer of copper and gold, respectively(1-3). The magnetic properties of cobalt films seem to be particularly sensitive to copper overlayers-deposition of o nly sub-monolayer amounts of copper will decrease the coercive field r equired to invert the magnetization direction(4). Here we show that co pper coverages as small as three-hundredths of a monolayer are suffici ent to rotate by 90 degrees the magnetization of Co films up to 20 ato mic layers thick. This implies that the spins of about 500 cobalt atom s switch direction for each copper atom added. Adding more copper even tually switches the magnetization back to its original direction. This fine tuning of thin-film magnetism might be useful for developing sen sitive magnetic-field sensors, as well as for magnetic recording.