Spin-dependent transport properties of a tetra-coordinated Fe(II) spin-crossover complex

Abstract

Spin-crossover (SCO) complexes are being regarded as one of the most promising components of molecular spintronics, since they can exhibit different spin states (high-spin/HS or low-spin/LS) in response to external stimuli. Here, the electronic structure as well as the transport properties of a tetra-coordinated bis(formazanate) Fe(II) SCO complex have been investigated with the DFT + NEGF approach. From the calculated results, the transition between different spin states of the Fe(II) SCO complex is accompanied by a variation of the Fe-N bond length and the dihedral angle between the planes of the ligands. The I-V curves of the molecular junctions revealed that the SCO complexes in different spin configurations display significantly different bias-dependent characteristics. When the bias is above 0.1 V, the current through the HS-configured molecular junction increases rapidly and is significantly greater as compared to that in the LS configuration. Furthermore, the transport properties of the HS-state SCO complex are dominated by spin-up electrons, indicating a strong spin-filtering effect.