Spin-valve heads with self-stabilized free layer by antiferromagnet

We demonstrate the feasibility of a spin-valve read head using an adjacent antiferromagnetic (AFM) layer to provide a stabilization Held, eliminating the hard bias permanent magnet layer. The head stack consists of seed/AFM/CoFe/Ru/CoFe/Cu/CoFe (and/or NiFe)/Cu/IrMn/cap where the AFM is PtMn or IrMn. The abutted junction is about 0.1 μm wide at the free layer and no permanent magnet materials are used. Micromagnetic modeling indicates that a proper bias field is needed to have a stable head response. The bias field from the AFM layer can be modified by a nonmagnetic spacer layer between AFM and FM. The coupling field decays exponentially with the thickness of the spacer layer, consistent with a pinhole-dominated mechanism. Unshielded sensors show much higher sensitivity as,compared with a standard PM abutted junction head. Microtrack profile based on the spin-stand test shows a regular shape without apparent lumps. The electrical reader width is about 6 μ" (0.15 μm), corresponding to a track density of 112 ktpi. Combined with a linear density of 591 kbpi the heads in this work are capable of areal density around 66 Gb/in².