Effects of gas damage on coupling and anisotropy in sputtered Co Cu multilayers

The giant magnetoresistance (GMR) of sputtered Co/Cu multilayers is reduced when they are not grown in clean vacuum conditions and earlier work has sh own that the most easily damaged parts of the multilayer are the Cu spacer layers. We have prepared samples with clean and dirty spacers and examined the magnetisation reversal mechanism as a function of applied field directi on by the magneto-optic Kerr effect and Lorentz electron microscopy. Whilst an uniaxial anisotropy is induced during the growth process, its effect on clean films with high GMR is small. By contrast the low field behaviour of low GMR gas damaged films is highly anisotropic. Quite different domain co nfigurations are observed in the two kinds of film, indicative of different dominant coupling mechanisms. (C) 1999 Elsevier Science B.V. All rights re served.