Unconstrained magnetism in nanostructures at zero temperature: An ultimate goal

Abstract

Recent calculations have shown that the magnetization of nanostructures cannot be safely described by collinear models based on phenomenological Ising Hamiltonian or electronic structure approaches. When interactions between spins are screened by electronic clouds, a Heisenberg Hamiltonian presents a safe approach for ground state calculations as well as for the determination of temperature dependant magnetization. In metallic systems, due to strong interactions between spins, semi-empirical models like Extended Hu ¨ckel, tightbinding or Periodic Anderson Model (PAM) have been used. Within these oversimplified approaches, vector magnetization could be tested and, for nanostructures, it generally led to non-collinear ground states. Ab initio calculations based on Kohn-Sham techniques can also describe non-collinear ground states but, because these techniques work in k-space, periodicity is necessary. This is a strong approximation for nanostructures. Therefore, in the present short review, we essentially focus on non-collinear magnetism of nanostructures by means of PAM approaches.