Spin-valve heads utilizing antiferromagnetic NiO layers

Spin-valve heads utilizing antiferro-magnetic NiO layers as the pinning layers were investigated. Advantages of using NiO are (1) superior corrosion resistance, (2) relatively high blocking temperature and (3) reduction in the heat generation due to current shunting. Spin-valve films of a structure of NiO/NiFe/Cu/NiFe show large Delta rho/Delta (approximately 4%) and good sensitivity. Thin Co layers inserted between NiFe and Cu improve both Delta rho/rho and the thermal stability. To explore the feasibility of spin-valves with NiO, unshielded sensors with hard bias structure having longitudinally magnetized permanent magnets were fabricated. Irregular response in the transfer curves can be suppressed when the permanent magnet strength M(r)t is 0.5 memu/cm(2) or more. The linear response region of the spin-valve sensor was optimized by adjusting the thickness of the pinned layers and the sensor height. Finally, by incorporating these results a shielded spin-valve head with a track width of 2.4 mu m, a gap length of 0.3 mu m and a sensor height of 0.7 mu m was fabricated. The response was noise-free and the output obtained with a small sense current of 0.41mA was approximately 1mVp-p, demonstrating a high sensitivity of a spin-valve head utilizing NiO.