Quantum size effect on the magnetism of finite systems

The magnetic moments of the ferromagnetic transition metals Fe, Co, and Ni confined to one-dimensional chains are found to fluctuate with increasing chain length before converging to the infinite limit. This quantum size effect is derived from a simple first-principles theory that we have developed to study the evolution of the electronic structure of systems as a function of size and dimensionality. The quantitative accuracy of the predictions of this simple formulation is confirmed by carrying out ab initio self-consistent calculations using the molecular-orbital approach. The convergence of moments to the respective infinite limit is found to depend on the dimensionality of the system.