Giant Magnetoresistance in Exchange-Biased Spin-Valve Layered Structures and its Application in Read Heads

Abstract

Exchange-biased spin-valve layered structures consist (in their simplest form) of a magnetically soft ferromagnetic layer, separated by a nonferromagnetic layer from a second ferromagnetic layer, which has its magnetization pinned by the exchange biasing interaction with a third magnetic (usually antiferromagnetic or ferrimagnetic) layer. For suitable layer compositions and nanometer-scale layer thicknesses these materials combine a fair Giant Magnetoresistance (GMR) effect with a very small field interval close to zero field in which the resistance change takes place. The resulting high sensitivity makes these materials attractive for sensor applications and other magnetoelectronic devices. In this overview, I first review experimental results on GMR of these materials, their theoretical interpretation, and the magnetic interactions which determine the magnetization reversal process. Subsequently, trends in magnetic recording and the potential benefit of exchange-biased spin-valves in yoke-type read heads for high-density digital magnetic recording are discussed. The chapter closes with an overview of unresolved issues, and with a note added in proof on developments that have taken place after the completion of the manuscript.