Tuning the magneto-transport properties of nickel-cyclopentadienyl multidecker clusters by molecule-electrode...

Spin transport in a series of organometallic multidecker clusters made of alternating nickel atoms and cyclopentadienyl (Cp) rings is investigated by using first-principles quantum transport simulations. The magnetic moment of finite NinCp(n+1) clusters in the gas phase is a periodic function of the number of NiCp monomers, n, regardless of the cluster termination and despite the fact that the band structure of the infinite [NiCp]infinity chain is nonmagnetic. In contrast, when the clusters are sandwiched between gold electrodes, their spin polarization is found to strongly depend on the molecule-electrode coupling. On the one hand, a substantial magnetic moment and a large spin polarization can be detected for NiCp2 and Ni4Cp5 with both weak and modest molecule-electrode coupling. On the other hand, when the coupling of the clusters is strong and mediated by Ni adatoms, the spin polarization of all NinCp(n+1) (n = 1-4) clusters is destroyed, although their low-bias conductance is large. This demonstrates that the magnetism and the spin-transport properties of fragile molecular magnets, such as NinCp(n+1), can be tuned in a controllable way by changing the contact geometry.