Preface to volume 12

Abstract

This chapter presents the preface to Handbook of Magnetic Materials, Volume 12. This publication discusses the giant magnetoresistance (GMR) effect used in various types of device, such as sensors, read heads, and magnetic RAM. The GMR is a prominent example of expansion of magnetism. The GMR of multilayers is induced by the variation of the angle between the magnetization of consecutive magnetic layers and its discovery was preceded by the discovery of exchange coupling between magnetic layers across a non-magnetic metal layer. Under certain circumstances the coupling is antiferromagnetic and induces an antiparallel alignment of the magnetization of adjacent magnetic layers. When an external magnetic field aligns the magnetization of all magnetic layers in parallel, there is a giant decrease of the resistance of the multilayer. The discovery of interlayer exchange and GMR has lead to an enormous proliferation of experimental and theoretical studies on multilayers and on magnetic nanostructures. GMR effects are observed in exchange coupled magnetic multilayers and also in uncoupled multilayers, spin valve structures, multilayered nanowires, and granular systems.