In the last decade, the discovery of giant magnetoresistance (GMR) effects in metallic multilayers has led to significant advancements in both basic research and engineering applications. A notable review edited by Hartmann in 1999 provides insights into the experimental and theoretical aspects of GMR studies, including magneto-optics and applications in electronic data storage. This overview focuses on the electronic applications of GMR, particularly in sensors and memories for magnetic data storage, which are of primary interest to electronic engineers. The GMR effect arises when the mean free path of conduction electrons exceeds the multilayer period, resulting in a resistance change due to the alignment of magnetizations in adjacent magnetic layers. In a low applied magnetic field, these magnetizations are antiparallel, but they shift to parallel alignment under the influence of the magnetic field, leading to reduced resistance in the saturation field. This phenomenon is influenced by RKKY-like magnetic coupling between adjacent magnetic layers through a nonmagnetic conductive layer.
