Shape and size effects in nanostructured 2D magnetic systems

The magnetization process of magnetic particles, including 2D arrays of nanosize patterns, strongly depends on the shape and size of elements. For a finite size body in the shape of an ellipsoid of rotation the magnetization M and the demagnetizing field H-Di = - NijMj can be considered uniform all over the body. For non-ellipsoidal shapes the demagnetizing "factor" becomes a local tensor N-ij = N-ij (r) and the magnetization is no more uniform M = M(r). Results of numerical modeling of the shape and size dependence of the demagnetizing tensor elements are presented for particles having a width-to-height ratio range from 0.01 to 10, calculated using the finite-difference method. This effect becomes increasingly important for arrays of nanosize particles with an aspect ratio in this range. The demagnetizing effects are the most pronounced at the corners and edges. As a result, it prevents full saturation of particles in applied fields even in H-z greater than or equal to 4 pi M-s, and contributes to substantial in-plane components acting on the neighboring particles. (C) 1999 Elsevier Science B.V. All rights reserved.