Spin Logic Gates Operated by Protonation and Magnetism in Molecular Combinational Circuits

Design of multifunctional spin logic gates based on manganese porphyrin molecules connected to graphene electrodes

The spin-resolved transport properties of molecular logic devices composed of two Mn porphyrin molecules connected to each other via a six-carbon atomic chain were studied using the non-equilibrium Green's function combined with density functional theory. The molecules were symmetrically connected to armchair graphene nanoribbon electrodes through four-carbon atomic chains on the left- and right-hand sides. Our calculations revealed that the spin-resolved current-voltage curves depend on the initial spin setting of the transition metal Mn atoms and carbon atoms on the zigzag edges where the electrodes come in contact with the molecule. By simultaneously regulating the spin orientations of the intermediate functional molecules and the zigzag edges of the armchair graphene nanoribbon electrodes, seven spin polarization configurations were obtained. These configurations were examined in this study considering the spin-related symmetry of molecular junctions. By meticulously selecting different combinations according to the specific input and output signals, YES, NOT, OR, NOR, and XOR multifarious spin logic devices were created. The findings of this study are expected to contribute toward the extension of molecular junction functions in future spintronic integrated circuit design and further miniaturization.

The emergence of the local moment molecular spin transistor

Local moment molecular systems have now been used as the conduction channel in gated spintronics devices, and some of these three terminal devices might even be considered molecular spin transistors. In these systems, the gate voltage can be used to tune the molecular level alignment, while applied magnetic fields have an influence on the spin state, altering the magnetic properties, and providing insights to the magnetic anisotropy. More recently, the use of molecular spin crossover complexes, as the conduction channel, has led to devices that are both nonvolatile and have functionality at higher temperatures. Indeed, some devices have now been demonstrated to work at room temperature. Here, several molecular transistors, including those claiming to use single molecule magnets (SMM), are reviewed.