Spin Filters, Spin Valves, and Reconfigurable Logic Gates Realized in a Dual-Gate-Controlled Bipolar-Magnetic-Molecule Junction

The continuous miniaturization of electronic components drives the exploration of molecular-scale devices capable of performing complex computational functions. Harnessing the spin degree of freedom in single molecules offers a promising path toward multifunctional spintronics. Here, we theoretically design a single-molecule device with dual-gate-controlled multiple functionalities based on a bipolar magnetic molecule (BMM), in which two nickelocene (NiCp 2 ) groups are serially connected with alkyl chains. Using density functional theory (DFT) combined with the nonequilibrium Green’s function (NEGF) method, we show that independent gate voltages applied to each NiCp 2 group enable precise control over the alignment of their spin-polarized frontier orbitals with respect to the Fermi level. Under symmetric gate voltages (−4, −4 V) or (6, 6 V), the device delivers nearly 100% spin-up or spin-down polarized current, functioning as a polarization reversible spin filter. Under asymmetric gate voltages (−4, 6 V) or (6, −4 V), opposite spin polarizations on the two NiCp 2 groups induce spin blockade, resulting in a spin valve with an ON/OFF ratio reaching as high as 7.4 × 10 3 . Furthermore, by redefining the two gate voltages as binary inputs, the device performs XNOR logic when using the total current at 0.1 V as output, and AND logic when using the spin-up current as output. Additionally, pronounced negative differential resistance (NDR) is observed under symmetric gate voltages, with peak-to-valley ratios exceeding 40. This work establishes NiCp 2 -based junctions as versatile platforms integrating spin filtering, spin valve, NDR, and reconfigurable logic, offering a pathway toward adaptive molecular spintronic circuits.