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Spin-valve (SV) heads with antiferromagnetic control layers for 20 Gbit/inch 2 recording were designed by solving the Landau-Lifshitz-Gilbert equation. The calculated SV-head model has a read track width of 500 nm and a detected minimum bit length of about 50 nm recorded on a medium whose thickness, t mag , is 14 nm, and the product of remanent flux density, B r , and thickness, t mag , is 50 Gµm. The head-to-medium spacing is 30 nm. When the sensing-current density is less than about 5.0 × 10 7 A/cm 2 , the thickness of the pinning layer and the free layer is appropriate to be 2.0 nm and 3.0 nm, respectively. The resolution, V high /V low , is about 0.67 when the optimum shield gap length, G, is 80 nm. The resolution depends on the sensingcurrent density, J , as well as the gap length G. We obtained a low-density output voltage of 700 µV p-p , which is practically applicable, by selecting the optimum element size.

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