Micromagnetics of laminated Permalloy films

The edge curling wall (ECW) is observed in an optical Kerr microscope. Conditions are derived energetically favoring single transverse domains with ECWs over other multiple closure domains or single longitudinal domains that are undesirable because of their low permeability. Computed figures illustrate how the maximum permissible spacer thickness depends on Permalloy sublayer thickness, uniaxial anisotropy, width of the magnetic strip, mismatch of Permalloy thickness, and perpendicular anisotropy. The case with strip width W=100 mu m and vanishing magnetostriction or stress should require only a few sublayers. However, if W is very small, or if stress-induced or some other form of perpendicular anisotropy is excessive, then attainment of single transversely magnetized domains requires many sublayers. Some of these conclusions are supported by microscopic observations.