Spin valve giant magnetoresistive sensor materials for hard disk drives

Abstract

Today virtually all recording heads in hard disk drives (HDD) use spin valve structures that employ giant magnetoresistance (GMR) to read back the magnetic information recorded in magnetic transitions on the hard disk. Introduced into products in 1997, remarkably soon after the discovery of the effect in 1988, they are produced economically by the hundreds of millions annually, and were a key factor in making possible the rapid storage areal density increase in HDD of the last 5 years. Spin valve structures are layered structures with layers only a few nanometers thick, and consist of a free magnetic layer, a conducting spacer layer, and a second magnetic layer whose magnetization is pinned by an antiferromagnet. Relative resistance changes in excess of 10% or larger are typical for spin valves used in devices. The fundamental physics of spin valves, structural details, operation and a variety of variants are discussed [6.1].