The relentless demand for smaller, faster, cheaper, more capable computers continues to drive the development of devices for sensing and storing information. Over the past decade, manufacturers have exploited the phenomenon of giant magnetoresistance (GMR) to build sensors for reading data bits coded as tiny magnetized regions on disk drives. The higher sensitivity of these GMR read heads to magnetic fields has allowed a reduction in the bit size and hence an enormous increase in the storage capacity of magnetic hard disk drives.