Spin-Crossover and Coherent Transport Behaviors of a Six-Coordinate Iron(II) Complex with a N₄O₂ Donor Set

Abstract

Single-molecule spin-crossover (SCO) complexes have been considered to be the promising candidates to design molecular spintronic devices due to their magnetic bistability between the high-spin (HS) and low-spin (LS) states. By performing extensive density functional theory calculations in combination with the nonequilibrium Green function method, we explore the SCO and coherent transport behaviors of a six-coordinate Fe(II) complex with a N 4 O 2 donor set. The calculated relative total electronic energies imply that the spin transition between the HS and LS states can be achieved by external stimuli in experiments via changing the metal−ligand bond lengths. Based on the calculated transport results, we find that the current through the six-coordinate Fe(II) complex with the LS state sandwiched between gold electrodes is significantly less than that of the HS state due to their significantly different electronic structures. Moreover, the molecular junction with the HS state displays a robust spin-filtering effect, and the current under the small bias voltage is dominated by the spin-down electrons. Interestingly, we observe that the transport properties of this examined Fe(II) complex with the HS and LS states are not sensitive to the detailed anchoring configuration, which is highly desirable in molecular spintronics. These theoretical findings suggest this Fe(II) SCO complex holds great potential in molecular spintronic devices.

Deposition of the Spin Crossover FeII–Pyrazolylborate Complex on Au(111) Surface at the Molecular Level

“…All the atoms were represented by a double‐zeta polarized (DZP) basis set, along with Troullier–Martins pseudopotentials, [65] employing the PBE exchange‐correlation functional, due to convergence problems found when using the rPBE functional with TRANSIESTA code. Moreover, PBE is the functional most used for evaluating the transport properties on molecular junctions through the DFT‐NEGFT methodology, [66–68] employed in several recent studies with Fe‐SCO complexes as magnetic active elements [69–73] …”

Tuning the spin caloritronic transport properties of InSe monolayers via transition metal doping

“…This transport behavior governed by the spin-down electrons has been commonly observed in single molecular Fe-based magnets, such as a six-coordinate Fe( ii ) complex with an N 4 O 2 donor set and the ligand-driven light-induced spin-change Fe-based spin crossover complexes. 38,39…”

“…This transport behavior governed by the spin-down electrons has been commonly observed in single molecular Fe-based magnets, such as a sixcoordinate Fe(II) complex with an N 4 O 2 donor set and the ligand-driven light-induced spin-change Fe-based spin crossover complexes. 38,39 This remarkable difference of thermal current between the spin-up and spin-down electrons under the applied temperature bias can be quantified by the thermal spin filtering efficiency (Z, TSFE) defined as Z ¼ ðjIð"Þj À jIð#ÞjÞ ðjIð"Þj þ jIð#ÞjÞ Â 100%.…”

Sublimable Spin‐Crossover Complexes: From Spin‐State Switching to Molecular Devices

“…Another interesting aspect of the SCO‐based metal/SCO molecule/metal junction is the ability of the HS‐state to mediate spin‐polarized transport upon charge injection from the nonmagnetic metallic electrode. Thus, the HS molecule could act as a spin valve/filter—a fundamental spintronics element [158–160] . Apart from the electronics and spintronics applications, the elastic nature of the SCO complexes is utilized to build nanoscale actuators and resonators [11] .…”