We present a first-principles study of the electronic and transport properties of linear clusters ${\mathrm{Mo}}_2{X}_2$ ($X=\mathrm{Fe}$,Co,Ni), formed by two $X$ atoms separated by a nearly nonmagnetic Mo dimer, connected to gold electrodes. Density functional theory, as implemented in the siesta code with the generalized gradient approximation, is used to determine the spin-polarized electronic structure of the molecular contact for relaxed distances. We show that the ${\mathrm{Mo}}_2{X}_2$ clusters anchored to the gold electrodes have two different magnetic states, corresponding to the spin isomers found in the freestanding environment, one of which has parallel magnetic coupling between the $X$ atoms across the Mo dimer and another that has antiparallel coupling. The transmission coefficients, current-voltage characteristics, and conductivity are then computed with the smeagol code for the two magnetic states. We show that this system presents spin-filtering properties and magnetoresistance driven by the magnetic state of the molecular contact.

• Received 30 November 2011

DOI:https://doi.org/10.1103/PhysRevB.85.224433