Dependency of coercivity on Co layer thickness in Co/Cu multilayer structures

The magnetic and structural properties of Co/Cu multilayered film structures were studied as a function of Co layer thickness to determine the interrelationship between coercivity and ferromagnetic layer thickness. The nominal compositions of the films are NiFe(50 Å)/Cu(2500 Å)/[Co(t)/Cu(50 Å)]x, where t=7, 10, 25, 50, 100 Å for x=20, and t=200, 400, and 2000 Å for x=10, 5, and 1, respectively. The measured coercivity correlates strongly with the changes in the local structural properties of the Co layers. Values were found to decrease with increasing t for t<200 Å in response to the decreasing effect of surface and interface domain wall pinning. For t⩾200 Å coercivity values increase corresponding with the increased magnetocrystalline anisotropy associated with a transition in the Co layer from an fcc state to an hcp state