Low-resistance IrMn and PtMn tunnel valves for recording head applications

We have investigated the use of ultrathin Al2O3 barriers to fabricate low-resistance tunnel-valve sensors suitable for recording heads. Tunnel valves of the type underlayer/(IrMn or PtMn)/CoFe/Al2O3/CoFe/NiFe/Cap layer have been fabricated by magnetron sputtering. Tunnel barriers are formed by Al metal deposition followed by in situ oxidation, and tunnel-junction test devices are built by photolithography with areas down to 1×1 μm2. Specific resistances as low as 13 Ω μm2 with 25% tunnel magnetoresistance have been obtained using Al thicknesses of 6–7 Å.