Antiparallel pinned NiO spin valve sensor for GMR head application (invited)

NiO antiferromagnetic material possesses certain advantages for spin valve applications and has attracted considerable attention. Some of the key adva ntages are its insulating properties, very high corrosion resistance, less sensitivity to composition, and its low reset temperature. This material, h owever, has a low blocking temperature which prevents its application to si mple spin valve designs. The use of this material in spin valve structures required significant improvements in thermal stability, blocking temperatur e, and the spin valve design. In the present study, the blocking temperatur e and the blocking temperature distribution of the NiO films have been impr oved by depositing the films reactively using ion beam sputtering. A number of improvements in the processing method and deposition system had to be m ade to allow full NiO spin valve deposition for mass production. Another cr itical part was the use of antiparallel pinned design in place of the simpl e design to improve the thermal stability of the NiO spin valves as read el ements at disk drive temperatures. The selection of the ferromagnetic pinne d layers and the Ru spacer thickness in AP-pinned spin valves has significa nt impact on the behavior of the devices. These spin valves are all bottom type, NiO/PL1/Ru/PL2/Cu/Co/NiFe/Ta, where the metallic portion of the spin valve is deposited on top of the NiO AF layer. The PL1 and PL2 are ferromag netic layers comprising NiFe and Co layers. Read elements have been made us ing these spin valves that delivered areal densities of 12 Gbit/in. These t opics and other improvements which resulted in successful use of NiO spin v alves as GMR heads in hard disk drives will be discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)73308-1].