Half-metallic porphyrin-based molecular junctions for spintronic applications

Abstract

Single molecular magnets (SMMs) have become promising paradigms to develop novel spintronics for futuristic information technologies such as high-density information and quantum computing. The efficiency and characteristics of SMM devices are determined by the intrinsic nature of the molecular magnets placed in the spin transport pathway. In this work, to understand the role of the central magnetic ion on the performance of SMM devices, we screen the spin-conductance properties of whole $3d$ and $4d$ metalloporphyrins using the nonequilibrium Green's function formalism in conjunction with density functional theory. Our results show that the investigated SMMs according to spintronic conductance behavior can be categorized into three groups: type I non-spin-polarized, type ${\mathrm{II}}^{\ensuremath{'}}$ minor spin-polarized current, and type ${\mathrm{II}}^{\ensuremath{''}}$ major spin-polarized current devices. Type-${\mathrm{II}}^{\ensuremath{'}}$ and type-${\mathrm{II}}^{\ensuremath{''}}$ 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 ${\mathrm{II}}^{\ensuremath{'}}$ and major for type ${\mathrm{II}}^{\ensuremath{''}}$). Thus type-II junctions are half-metal. The type-${\mathrm{II}}^{\ensuremath{''}}$ 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, memory, to name just a few. Our results highlight the practical applications of metalloporphyrin for the development of multipurpose miniature spintronic devices.