A GMR multilayer structure used as a magnetic head. Typically, a GMR head consists of a stack of four magnetic thin layers with nanometre thicknesses: a sensing or free magnetic layer, a nonmagnetic spacer layer, a magnetically pinned layer, and an antiferromagnetically coupled exchange layer. The free layer changes its magnetization direction in response to magnetic fields from the storage bits, while the magnetization of the pinned layer is fixed. Thus a change in the resistance of the GMR head depends on the difference in the magnetization directions of the free and pinned layers. Compared with conventional magnetic heads, the increased signals from GMR heads have led to an increase of the storage density of magnetic recording by 20 times. The high areal densities attainable with GMR heads enable hard-drive products to offer maximum storage capacity with a minimum number of heads and disks. Fewer components also lead to greater reliability and lower power consumption.