2. Ferromagnetism of nanostructures

2.1 Energy in continuous media

The description of the magnetic properties of nanostructures is based on the continuous media approximation. Leaving aside the discrete, quantum nature of magnetic moments, the set of magnetic moments is described by a spatially continuous function known as the magnetization M. This is a vector measuring the magnetic moment per unit volume, expressed in A.m ^-1 . Generally speaking, the magnetization of a ferromagnetic system depends on both space and time M(r, t), but remains a constant-norm vector: