Anisotropic Coupling in Hexagonal Arrays of Asymmetric Nickel Nano-Rings

Here we report experimental studies of the orientational effects due to anisotropic coupling in hexagonal arrays of asymmetric Ni nano-rings. The remanent magnetization and coercive field were examined as a function of applied field angle in two samples with different orientations of asymmetry of the shape with respect to the principal axis of the lattice. It was found that the angular variation of coercive field follows a two-fold symmetry while the remanence exhibits a four-fold variation. The four-fold variation is more pronounced when the symmetry axis of the shape is in the same direction as the principal axis of the lattice. As seen from micromagnetic simulations the coupling arising from closely packed elements in a hexagonal array does not significantly affect the "vortex" state, but it does affect the remanent state of the system. Here we show that by changing the direction of the symmetry of the ring with respect to the lattice orientation one can manipulate the hysteretic dependence of the system.