Transmission Lorentz microscopy of two-layered Co80Nb10Ti10films

Magnetic domain structures in two layered 300-550 A thick Co80Nb10Ti10films with magnetostatic coupling across nonmagnetic layer with thickness d from 8 to 800 A were examined through transmission Lorentz microscopy at 200 kV. At d= 20 A the coupling of two layers is strongest and two layers are magnetized in parallel direction except the coupled Néel wall regions. At d=40-160 A domains in two layers are magnetized in independent directions but strong coupling between the domain walls in both layers causes complicated domain configuration. The characteristic vertical pair domains and 90° walls play a role to result flux closure between the layers. The maximum thickness of 180° wall reaches 4000 A at this d range.