We have investigated the performance of dual spin valve heads in the current-perpendicular-to-plane (CPP) geometry on dynamic electrical tests (DET) and quasi-static tests (QST). Shielded CPP reader and stitched pole writer composite heads were fabricated. A various physical read track width and area of the dual spin valve element were deliberately obtained in the range of 41-175 nm and 0.0034-0.022 m 2 , respectively. Materials used for the CPP dual spin valve are Co 90 Fe 10 , Ni 80 Fe 20 , Cu, Ru, Ta, and Pt 50 Mn 50 , which are common in industrial current-in-plane (CIP) spin valves. The shape and smoothness of QST transfer curve, readback waveform, micro-track, and full-track profiles of the narrow read track CPP heads are essentially just the same as those of CIP spin valve. A track-average-amplitude of 0.6 mV was obtained at the bias current density of element around 100 MA/cm 2 in the CPP head with the physical read track width of 47 nm. Overall reader resistance of the CPP heads at head gimbals assembly (HGA) level was in the range of 10-35 and proved to be well appropriate.Index Terms-Current-perpendicular-to-plane (CPP) geometry, giant magnetoresistance, narrow track, spin valve head.

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Spin valve films with a laminated antiparallel Co/NiFe/Ru/NiFe synthetic ferrimagnet (SF) free layer combined with PtMn/Co/Ru/Co SF pinned layers were demonstrated to maintain large magnetoresistance ratio of ∼8.0% even below ∼10 Å of effective thickness of the Co/NiFe/Ru/NiFe SF free layers, defined as the thickness difference of the two ferromagnetic layers antiferromagnetically coupled through Ru. Spin flopping field Hsf and saturation field Hs of the Co/NiFe/Ru (8 Å)/NiFe SF free layers slightly increased after annealing at 250 °C for 4 h, and then the Hsf of the Co (3 Å)/NiFe(30 Å)/Ru(8 Å)/NiFe(20 Å) SF free layer after annealing remained 600 Oe, even at 200 °C. Further, antiferromagnetic coupling interlayer materials and their thickness dependence of Hsf and Hs were investigated in the Co(3 Å)/NiFe(40 Å)/X/NiFe(25 Å), X=Ru, Cr, Ir, and Rh, sandwich stacks. The oscillatory antiferromagnetic exchange coupling was clearly observed, and the large Hsf and Hs exceeding 2000 Oe and 7 kOe, respectively, were obtained both at Ir 3.8 Å and Rh 6.1 Å, which corresponded to the oscillatory first peak in the Co/NiFe/Ir/NiFe and Co/NiFe/Rh/NiFe sandwiches.

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