An integrated multi-rack read/write head and associated circuitry suitable for high performance (100 MHz), ultra-high density (2x109 bits/in2) recording will be designed. The magnetoresistive sensor wil use Giant Magnetoresistance Ratio (GMR) material, which provied a much higher signal (about ten times) compared with standard materials because of higher magnetoresistance and higher sheet resistivity. The orientation of the sensor wil be orthogonal to the orientation of the sensors in use today for improved reliability and higher density. The associate circuitry will be signed using CMOS on a substrate of Silicon on Sapphire (SOS) which has both favorable wear capability compared to silicon, and in addition has lower parasitic capacitances that silicon, hence improving the electrical performance of the on-chip circuitry. Sensors for servo track will be included in the design. In Phase I the head will be designed, and satisfactory GMR materials will be demonstrated on a substrate comprised of permalloy shielding material on SOS. The read portion on the head designed in Phase I, except for shields, will be fabricated and demonstrated in Phase II.