SPIN-VALVE HEADS UTILIZING ANTIFERROMAGNETIC NIO LAYERS

Spin-valve heads utilizing antiferro-magnetic NiO layers as the pinnin g layers were investigated. Advantages of using NiO are (1) superior c orrosion resistance, (2) relatively high blocking temperature and (3) reduction in the heat generation due to current shunting. Spin-valve f ilms of a structure of NiO/NiFe/Cu/NiFe show large Delta rho/Delta (ap proximately 4%) and good sensitivity. Thin Co layers inserted between NiFe and Cu improve both Delta rho/rho and the thermal stability. To e xplore the feasibility of spin-valves with NiO, unshielded sensors wit h hard bias structure having longitudinally magnetized permanent magne ts were fabricated. Irregular response in the transfer curves can be s uppressed when the permanent magnet strength M(r)t is 0.5 memu/cm(2) o r more. The linear response region of the spin-valve sensor was optimi zed by adjusting the thickness of the pinned layers and the sensor hei ght. Finally, by incorporating these results a shielded spin-valve hea d with a track width of 2.4 mu m, a gap length of 0.3 mu m and a senso r height of 0.7 mu m was fabricated. The response was noise-free and t he output obtained with a small sense current of 0.41mA was approximat ely 1mVp-p, demonstrating a high sensitivity of a spin-valve head util izing NiO.