Hitachi GST has continually developed new magnetic read/write sensors for use in disk drives. Today's heads consist of an advanced inductive write element merged with a GMR (giant magnetoresistive) read sensor to achieve high data densities and performances. Hitachi GST pioneered the SAL (soft adjacent layer) MR (magnetoresistive) structure as well as the antiferromagnetic exchange film GMR structure. The latter was introduced in a 1997 HGST (IBM) disk drive. Hitachi GST is experimenting with newer head designs, including CPP (current perpendicular to the plane) as an evolutionary trend derived from the present CIP (current in plane). This modification is consistent with smaller read widths at higher areal densities. At these densities, resistance changes in the head originating from the GMR effect are reduced based on the progressively smaller dimensions of the length of the GMR read head. In the present in plane read head structure (CIP), electrical current flows between contacts parallel to the disk surface. Redesigning the head so that current now flows through the films, perpendicular (CPP) to the long axis of the structure and normal to the disk surface results in a significant resistance change with disk magnetic field. This occurs even at very small read head lengths.

In write head development, it is reasonable to assume that future head technologies could include perpendicular recording in which an entirely new write head design could be used in Hitachi GST disk drive products to achieve even higher data densities while maintaining excellent thermal stability in the media.