Spin filtering through a metal/organic-ferromagnet/metal structure

Spin filtering in a metal/organic-ferromagnet/metal sandwich device was investigated based on an extended $\mathrm{SSH}+\text{Heisenberg}$ ($\mathrm{SSH}=\mathrm{Su}$-Schrieffer-Heeger) model and the Landauer-Büttiker formula. A large spin-polarized current was predicted, which is dependent on the property of the organic ferromagnetic interlayer as well as the interfacial interactions between the metal electrode and the organic ferromagnet. The effect of thermal fluctuation of the radical spins on the current polarization is discussed. Our investigation suggests a possible application of an organic ferromagnet in a spin filter device without any external field modulation.

Figure 1

The simplified structure of a metal/organic-ferromagnet/metal nanojunction.

Figure 2

(a) The calculated current-voltage characteristics of our model device. (b) Spin polarizations of the currents as a function of bias.

Figure 3

The density of states (DOS) of the organic-ferromagnet molecule near the Fermi energy at a bias voltage of $0.8\mathrm{V}$.

Figure 4

Spin polarization versus spin-correlation strength $J$ at a bias voltage of $0.8\mathrm{V}$. The inset plot is the electronic density with different spins at $J=0.5$.

Figure 5

The current spin polarizations as a function of bias with different e-la coupling constants.

Figure 6

The dependence of spin polarization on the interfacial coupling parameter $t_{l\left(r\right)M,\uparrow }$ at a bias of $0.8\mathrm{V}$. Here, $t_{l\left(r\right)M,\downarrow }$ is fixed at $0.5\mathrm{eV}$. Other parameters are the same as those in Fig. 2.

Figure 7

The effect of orientation fluctuation of radical spins on the current spin polarization.