Dual Control of Spin Polarization Reversal in a Bipolar Magnetic Single-Molecule Spin Field-Effect Transistor

In this work, we have designed a single-molecule spin field-effect transistor (spin-FET) by utilizing a bipolar magnetic molecule (BMM) nickelocene undecanethiol (SC₁₁NiCp2) and investigated its spin transport properties by employing a first-principles quantum transport approach. In this BMM, the highest occupied molecular orbital (HOMO) and HOMO-1 are spin-up polarized while the lowest unoccupied molecular orbital (LUMO) and LUMO+1 are spin-down polarized. By modulating the polarity and magnitude of the bias or gate voltage, either spin-up (HOMO-1 and HOMO) or spin-down (LUMO and LUMO+1) orbitals can be brought close to the Fermi level, enabling a highly spin-polarized current through the device with the maximum spin filtering efficiency reaching 94% for spin-up polarized current and 96% for spin-down polarized current. Our work highlights the bipolar spin filtering characteristic of the single-molecule spin-FET controlled by the bias or gate voltage, showing promising applications in molecular spintronics, especially in single-molecule logic circuits.