Magnetic and transport properties of Fe-4 single-molecule magnets: a theoretical insight

Abstract

Here, methods of density functional theory (DFT) were employed to study the magnetic and transport properties of a star-shaped single-molecule magnet Fe-4 S = 5 complex deposited on a gold surface. The study devoted to the magnetic properties focused on changes in the exchange coupling constants and magnetic anisotropy (zero-field splitting parameters) of the isolated and deposited molecules. Molecule surface interactions induced significant changes in the antiferromagnetic exchange coupling constants because these depend closely on the geometry of the metal complex. Meanwhile, the magnetic anisotropy remained almost constant. Transport properties were analysed using two different approaches. First, we studied the change in magnetic anisotropy by reducing and oxidizing the Fe-4 complex as in a Coulomb blockade mechanism. Then we studied the coherent tunnelling using DFT methods combined with Green functions. Spin filter behaviour was found because of the different numbers of alpha and beta electrons, due to the S = 5 ground state.