Chapter 1 - GMR in Metallic Multilayers – A Simple Picture

Abstract

Publisher Summary The basic physics related to the giant magnetoresistance (GMR) effect is tied to the fact that the electron spin takes two different values (say up and down) and, when traveling through magnetized materials, one type of spin might encounter a resistance that is different from that experienced by the other. Thin metallic multilayers became the proving ground for the GMR effect because their magnetizations could be altered with some ease, especially in a sandwich structure. In this chapter, details can be found about the GMR effect, its discovery and history, magnetic recording as well as other related phenomena. This chapter discusses magnetoresistance, magnetic recording, perpendicular recording and future storage technology, and a historical perspective of GMR. There is a discussion about qualitative arguments including quantum well (QW) approach and spin-polarized quantum well states. There is discussion on growth related issues and measuring interlayer coupling, GMR in magnetic sensors, biquadratic coupling. The chapter also discusses selected multilayer systems—Co/Cu (001), multilayers grown on Fe whiskers, Fe/Cr system, multilayered alloys, and nanowires. There are details on scattering of electrons, magnetic tunnel junctions, and half-metallic systems. An introduction to the GMR effect has been provided. Some applications, such as magnetic recording, sensors, and multilayered nanowires are discussed briefly and with vivid examples. A picture of how the magnetic exchange interaction gets transmitted through the spacer layer is provided using quantum well ideas from elementary quantum mechanics. In addition, various related experimental systems are discussed and compared to theoretical calculations.