Theory of Tunneling Magnetoresistance and Its Application to Hard Disk Technology

Abstract

The significant increase in hard disk storage capacity since 2009 can be partly attributed to a theoretical prediction, based on realistic quantum mechanical models, made in 2001 by the authors. The prediction was that a layered system based on crystaline Magnesium Oxide (MgO) would lead to a huge increase in magnetoresistance, a physical property that determines the efficiency of hard disk read heads. In 2004 these theoretical predictions were confirmed experimentally; by 2008 the new type of read head based on MgO was manufactured commercially, leading to significant increases in storage capacity from GBs to TBs. Today all computer hard disks use this technology. In this article we review the story of this discovery and, using undergraduate quantum mechanics, we present a simple model of an MgO tunnel junction, which forms the basis of all hard disk read heads.