Effects of oxide seed and cap layers on magnetic properties of a syntheticspin valve

A synthetic spin valve comprising Al2O3/Ni-Cr-Fe/Ni-Fe/Pt-Mn/Co-Fe/Ru/Co-Fe /Cu/Co-Fe/Ni-Fe/Cu/Al2O3/Ta films has been annealed and evaluated as a read sensor for ultrahigh-density (greater than or equal to 20 Gb/in.(2)) recor ding. The Al2O3 film used as its oxide seed layer provides an in situ flat surface for the Pt-Mn, Co-Fe and Ni-Fe films to develop strong {111} crysta lline textures, thereby increasing its giant magnetoresistance coefficient to as high as 13.8%. Another Al2O3 film used as its oxide cap layer protect s the Co-Fe/Ni-Fe sense layers from interface mixing and oxygen interdiffus ion, thus improving the soft magnetic properties and thermal stability of t he sense layers. Antiferromagnetic/ferromagnetic coupling between the Pt-Mn pinning and Co-Fe/Ru/Co-Fe synthetic pinned layers is strong and thermally stable enough for proper sensor operation. Ferromagnetic/ferromagnetic cou pling across the Cu spacer layer is antiparallel, and hence it is feasible to achieve optimal biasing of magnetoresistance responses. This synthetic s pin valve is sandwiched into a read gap 0.1 mum in thickness, and is patter ned and lapped into a read sensor 0.42 and 0.23 mum in physical width and h eight, respectively. With a sense current of 4 mA, this read sensor exhibit s an effective read width of 0.31 mum, stable magnetoresistance responses, and signal sensitivity of 6.64 mV/mum. (C) 2001 American Institute of Physi cs.