Oxygen as a Surfactant in the Growth of Giant Magnetoresistance Spin Valves

W.F. Egelhoff, Jr., P.J. Chen., C.J. Powell, M.D. Stiles, R.D. McMichael, J.H. Judy,
K. Takano and A.E. Berkowitz.

Journal of Applied Physics 82(12), 6142-6151 (1997).

Abstract:

We have found a novel method for increasing the giant magnetoresistance (GMR) of Co/Cu spin valves with the use of oxygen. Surprisingly, spin valves with the largest GMR are not produced in the best vacuum. Introducing 5x10 -9 Torr (7x10-7 Pa) into our ultrahigh vacuum deposition chamber during spin-valve growth increases the GMR, decreases the ferromagnetic coupling between magnetic layers, and decreases the sheet resistance of the spin valves. It appears that the oxygen may act as a surfactant during film growth to suppress defects and to crate a surface which scatters electrons morespecularly. Using this technique, bottom spin valves and symmetric spin valves with GMR values of 19% and 24.8%, respectively, have been produced. These are the largest values ever reported for such structures.

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