Magnetic coupling in Gd/Ni bilayers

Layered thin films consisting of rare earth materials and magnetic transition metals reveal a variety of magnetic properties due to their complex coupling interactions. The Gd/Ni system adds its own features due to the interplay of saturation moments and Curie temperatures of these two metals. Magnetic coupling in Gd/Ni bilayers leads to negative remanence and interesting magnetic switching behavior, which is strongly temperature-dependent. A transition from the 'nickel-aligned' state to the 'gadolinium-aligned' state is observed at 45 K, independent of the chosen substrate and hence of the Curie point of the Gd layer, which depends on the substrate. In x-ray magnetic circular dichroism experiments a polarization of Gd moments at the interface antiparallel to the Ni layer was observed even at room temperature. Structural analysis show a rough Gd/Ni interface with grains of a few nm and an amorphous Gd growth is indicated by diffraction methods.