Spin re-orientation in magnetostatically coupled Ni80Fe20 ellipsoidal nanomagnets

We investigate the influence of magnetostatic coupling on the spin configurations and magnetization reversal mechanism in a one-dimensional linear chain of densely packed Ni80Fe20 ellipsoidal nanomagnets arranged in two basic configurations (elements coupled along the major or minor axes). Using magnetic force microscopy (MFM) we observed that for geometrically identical ellipsoidal nanomagnets the magnetic states at remanence are strongly dependent on the arrangement of the ellipsoid due to competition between the inherent shape and configuration anisotropies. When the elements are coupled along the major axis, the individual elements adopt a single domain magnetic state at remanence for field applied along the linear chain. This is in contrast with a wide range of magnetic states (single vortex states, double vortex states and modified single domain states) observed for elements coupled along the minor axis and also isolated elements. We have conducted a detailed investigation on the magnetization reversal mechanisms for both configurations and have correlated our experimental results with micromagnetic simulations.