Features of unidirectional magnetic anisotropy in multilayer nanostructured systems [Co–Al2O3]

Abstract We study the magnetic anisotropy of multilayer nanostructures [Co–Al 2 O 3 ] N with fixed Co island layer thickness ( d ≈ 1 . 2 nm ) and varying Al 2 O 3 layer thickness. We use the Kerr effect to measure the magnetization hysteresis loops at different orientations of the magnetic field. We observed a unidirectional magnetic anisotropy in structures with small thicknesses of Al 2 O 3 layers ( d 1 . 4 nm ) when the exchange interaction between the Co layers is large. This anisotropy was oriented at 150° with respect to the easy axis of a continuous Co film. We believe that the unidirectional anisotropy can be caused by the super-vortex magnetization of the multilayer structure, while the unidirectional magnetization is caused by the projection of the super-vortex core on the sample plane.