GIANT STEPS WITH TINY MAGNETS

Giant magnetoresistance (GMR) comprises one of today's hottest research topics in basic magnetism and is poised for application in a range of information storage technologies. GMR was discovered in magnetic multilayers: structures that contain alternate layers of a magnetic element, such as iron or cobalt, and a nonmagnetic element such as chromium and copper. Resistance in metals is caused by electrons being scattered from impurity atoms and lattice imperfections. Giant magnetoresistance is thought to be due to the spin dependence of this scattering; the amount of scattering, and hence the resistance, depends on whether the electron spins are parallel or antiparallel to the magnetization. The main technological interest of GMR lies in its ability to detect tiny magnetic fields. This may find applications in magnetic recording and the creation of a permanent magnetic random-access memory chips, among others.