Magnetic Anisotropy Energies of Metal-Benzene Sandwiches

We report on ab initio calculations of the electronic and magnetic properties of metal-benzene sandwiches M-n(C6H6)(m) (M = V, Nb, Ta) and infinite wires, obtained by an infinite repetition of metal-benzene half-sandwiches, based on the density functional theory (DFT) in the generalized gradient approximation (GGA). Because of the increasing influence of the spin-orbit interaction on the magnetic properties, as going from V to Ta, a significant increase of the magnetic anisotropy energy (MAE) in the molecules is observed. In particular, an infinite Nb-benzene wire is predicted to change its ballistic conductance upon changing of magnetization direction (ballistic anisotropic magnetoresistance). The origin of the peculiar magnetic properties of the molecules is analyzed, and new possible technological applications are proposed. (c) 2006 Wiley Periodicals, Inc