Top, bottom, and dual spin valve recording heads with PdPtMn antiferromagnets

We fabricated top-type (Substrate/free layer/Cu/pinned layer/antiferromagnetic layer) and bottom-type (Sub./antiferro/pinned/Cu/free) spin valve heads using PdPtMn antiferromagnets. Bottom type spin valve head with a buffer layer of Ta/NiFe showed similar exchange bias field and MR ratio as top-type spin valve head. Dual spin valve (DSV) films with two pinning layers of PdPtMn had an enhanced MR ratio by 40% compared to the top-type spin valve. Patterned DSV elements with 3 μm MR height showed relatively large deviation from the optimum bias state. In order to adjust the bias point, asymmetric DSV elements with Cu layers of different thicknesses were investigated. Asymmetric DSV with the structure of Ta/NiFe/PdPtMn/CoFe/Cu(t₁)/CoFe/NiPe/CoFe/Cu(t₂ )/CoFe/PdPtMn (t₁≠t₂) showed an improvement for just bias using sense current magnetic field. The possibility of reducing the PdPtMn critical thickness for exchange coupling was investigated using ultra high vacuum (UHV) deposition environment. UHV technique is significantly useful to obtain exchange bias field (H_ua) of PdPtMn(t)/ferro at t<15 nm. The thickness of pinning PdPtMn was reduced from 25 nm to 13 nm and we fabricated single spin valve with total thickness of 26.5 nm which exhibited large MR ratio over 8.0%, sufficient H_ua (>500 Oe), large sheet resistance change (Δρ/_total=1.6 Ω), and good thermal stability up to 300°C. The total thickness of DSV was also reduced from 80 to 53 nm. Single and dual spin valves with thin PdPtMn pinning layer are very promising sensors for ultra high density recording applications