Structure and magnetic properties of hexagonal arrays of ferromagnetic nanowires

Here we present a model that explains a number of the magnetic properties of arrays of cylindrical ferromagnetic nanowires. The model properly considers the magnetostatic contributions from the wire inhomogeneities, here taken as a chain of ellipsoidal grains, as well as the dipolar interactions summed in the overall array of hexagonal symmetry. Carrying out the complete sum of both the dipolar interactions between the ellipsoidal grains and between the nanowires, we obtain an analytical expression for the magnetostatic energy. The effective anisotropy field extracted from the magnetostatic energy predicts the change in the magnetization easy direction from parallel to perpendicular to the wire axis. The expressions contain information on microscopic parameters such as packing factor, length and diameter of the nanowires, and shape and size of the ellipsoids. The model has been used to interpret ferromagnetic resonance data of Ni nanowires fabricated by electrodeposition in porous anodic aluminum oxide membranes. (c) 2009 American Institute of Physics. [DOI: 10.1063/1.3074110]