Spin-filtering, giant magnetoresistance, rectifying and negative differential resistance effects in planar four-coordinate Fe complex with graphene nanoribbon electrodes

Effect of the linkage modes of thiolated ethynyl groups on the spin-dependent electronic transport properties in transition metal porphyrin molecular junctions

Using density functional theory and nonequilibrium Green's function method, the spin-dependent electronic transport properties of six transition metal porphyrin molecules (VP, CrP, MnP, FeP, CoP, and NiP), which are linked to gold electrodes through the thiolated ethynyl groups, are investigated. Two different linkage modes (beta linkage and meso linkage) of the substituted ethynyl groups on the porphyrin macrocycle are considered. The results show that the linkage mode of ethynyl groups plays an important role on the spin transport properties of the molecular junctions and the beta linkage is more favorable for the spin filtering efficiency of current than the meso linkages. The spin-up and spin-down energy levels show the different evolutions which is responsible for the difference of spin filtering efficiency between the two linkage modes. The computational results of total current show that the meso-linked molecular junctions have the better conductive performances than the beta-linked ones which may be caused by the different electronic transport paths.

Spin-filtering and tunneling magnetoresistance effects in 6,6,12-graphyne-based molecular magnetic tunnel junctions

In the present study, by cutting 6,6,12-graphyne along vertical and horizontal directions, two kinds of 6,6,12-graphyne nanodots (6,6,12-GYNDs) with different sizes are obtained. Using these 6,6,12-GYNDs, we theoretically designed two kinds of 6,6,12-graphyne-based molecular magnetic tunnel junctions (MMTJs) and investigated their spin-dependent transport properties. Depending on the orientation of the 6,6,12-GYNDs and the connection of the 6,6,12-GYNDs to electrodes, our results show that the two MMTJs have novel transport behaviors. Two different net spin currents can be obtained by tuning the spin configurations and the maximal order of magnitudes of tunneling magnetoresistance values of the two MMTJs reaches 106%. The high spin-filtering ratio and large tunneling magnetoresistance value provide high sensitivity for practical applications. Therefore, the spin-filtering and tunneling magnetoresistance effects enable 6,6,12-graphyne-based MMTJs to be used as spintronic devices.

Coherent transport through spin-crossover magnet Fe2 complexes

As one of the most promising building blocks in molecular spintronics, spin crossover (SCO) complexes have attracted increasing attention due to their magnetic bistability between the high-spin (HS) and low-spin (LS) states. Here, we explore the electronic structures and transport properties of SCO magnet Fe2 complexes with three different spin-pair configurations, namely [LS-LS], [LS-HS], and [HS-HS], by performing extensive density functional theory calculations combined with the non-equilibrium Green's function technique. Our calculations clearly reveal that the SCO magnet Fe2 complexes should display two-step spin transitions triggered by external stimuli, i.e. temperature or light, which confirm the previous phenomenological model and agree well with previous experimental measurements. Based on the calculated transport results, we observe a nearly perfect spin-filtering effect and negative differential resistance (NDR) behavior integrated in the SCO magnet Fe2 junction with the [HS-HS] configuration. The current through the [HS-HS] SCO magnet Fe2 complex under a small bias voltage is mainly contributed by the spin-down electrons, which is significantly larger than those of the [LS-LS] and [LS-HS] cases. The bias-dependent transmissions are responsible for the observed NDR effect. These theoretical findings suggest that SCO Fe2 complexes hold potential applications in molecular spintronic devices.

Nonequilibrium spin injection in monolayer black phosphorus

Nonequilibrium spin injection and spin-polarized quantum transport in monolayer black phosphorus are studied using the first principles method.

Spin-dependent transport properties of a chromium porphyrin-based molecular embedded between two graphene nanoribbon electrodes

By using the nonequilibrium Green's function formalism combined with the density-functional theory, we present a theoretical study of the spin-dependent electron transport of a chromium porphyrin-based molecule device.