Half-metallic porphyrin-based molecular junctions for spintronic applications*

Molecular spintronics, have become promising paradigms to develop nanoscale electronic circuits such as high-density information and quantum computing. The efficiency and characteristics of molecular spintronics are determined by the intrinsic nature of the molecular magnets placed in the transport pathway. Among the studied molecular magnets, metal porphyrins (MPors where M is a transition metal) as a building block of future molecular spintronics. In this work, computationally we screen the spin-conductance properties of 3d and 4d MPors using the nonequilibrium Green's function formalism. Our results show that MPor-based molecular junctions according to spintronic conductance behavior can be categorized into three groups: type I non-spin-polarized, type II′ minor spin-polarized current, and typeII′′ major spin-polarized current devices. Type-II′ and type-II′′ molecular systems show perfect spin filtering and spin-dependent negative differential resistance. The optimal energy alignment of spin-polarized molecular orbitals with gold electrodes results in one-channel spin transport (minor for type II′ and major for type II′′). The type-II′′ junctions also show a voltage-induced spin switchability at low bias voltages. In this regard, type-II molecular systems are promising candidates for a low-power consumption spin filter, spin switch, and memory. Our results highlight the practical applications of metalloporphyrin for the development of multipurpose miniature spintronics.