Elementary magnetoelectronics

The so-called giant magnetoresistance (GMR) effect is one of the few discoveries of basic physics and materials science that has netted industrial applications in as little as one decade. "Magnetoelectronics" is the technology that takes advantage of the additional functionality of metallic ferromagnets in electronic circuits and devices by employing the principles of the GMR and its derivates. The more catchy term of "spintronics" is often used to include, for example, single spin manipulations in nonmagnetic systems such as semiconductor quantum dots. This is often done with an eye on applications for "quantum computing." These and other exotic phenomena, such as macroscopic quantum coherence of magnetism, are outside the scope of this article. Here we will focus on the basic concepts of GMR-type of magnetoelectronics with ferromagnets.