Designing multifunctional single-molecule devices by mononuclear or binuclear manganese phthalocyanines

Abstract

Molecular-scale magnetic devices have attracted great attention of research in recent years. In this work, by using the non-equilibrium Green’s function (NEGF) method in combination with density functional theory (DFT), we investigated the spin transport properties of manganese phthalocyanine based spintronic devices constructed by a mononuclear manganese phthalocyanine (MnPc) or binuclear manganese phthalocyanine (Mn2Pc2) sandwiched between two zigzag-edge graphene nanoribbon (zGNR) electrodes. The calculation results show that both MnPc and Mn2Pc2 devices are good spin filters manifesting excellent spin filtering effect, which is originated from the distinct difference in the energy alignments of the spin-up and spin-down molecular electronic states with respect to the Fermi energy (EF) of zGNR electrodes. More interestingly, the spin polarization of the tunneling electrons through the devices is intimately opposite to that of Mn atom(s). Specifically, for a spin-up polarization of Mn in the devices, almost only the spin-down electrons are allowed to go through the device, and vice versa. In addition, spin filtering efficiency (SFE) of the devices is evidently enhanced in Mn2Pc2 devices in comparison with that of the MnPc devices, of which the value of SFE can reach almost 100%. This enhancement is attributed to the fact that the spin electronic states of Mn2Pc2 devices are closer to EF and there is a weaker localization in their spatial distributions induced by the external bias voltage. Furthermore, both MnPc and Mn2Pc2 devices can act as NOT logic gates by taking the spin polarization characteristics of Mn atom(s) and current of devices as input and output signals, respectively. This work demonstrates that mononuclear MnPc and binuclear Mn2Pc2 molecules have potential applications in designing multifunctional spintronic single-molecule devices.