Review of the Physics of Magnetoresistive Readers

The rapid increase in areal density storage capacity in magnetic hard disk drives over the past decade has, to a large extent, been enabled by advances in reader technologies. We will here review the underlying physics of spin valves and tunneling readers with an emphasis on the interplay between transport, magnetism, materials properties, and signal-to-noise. Finally, we will give a a brief outlook to some of the technologies currently under development for future readers.