Bipolar Magnetic Molecules for Spin-Polarized Electric Current in Molecular Junctions.

Electrical control of spin transport at single molecule level is highly desired for molecular nanospintronics. By exploiting magnetic bistability of spin crossover complexes, the magnitude of spin polarization can be modulated. However, efficiently controlling the direction of spin polarization at single molecule level is still challenging. Here, we propose a general method to flip the transport electron spin simply by electrical gating in single molecule devices based on bipolar magnetic molecules (BMMs), of which highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) come from different spin channels. Thus, when device's Fermi level is reversibly adjusted approaching either HOMO or LUMO by changing the polarity of applied voltage gate, a 100% spin polarized current with switchable spin direction is achievable. The proposed method is verified by the calculated electronic and transport properties of 9 potential transition metal coordination BMMs.