Giant magnetoresistance in the junction of two ferromagnets on the surface of diffusive topological insulators

We reveal the giant magnetoresistance induced by the spin-polarized current in the ferromagnet (F${}_1$)/ topological insulator (TI)/ferromagnet (F${}_2$) junction, where two ferromagnets are deposited on the diffusive surface of the TI. We can increase and reduce the value of the giant magnetoresistance by tuning the spin-polarized current, which is controlled by the magnetization configurations. The property is intuitively understood by the nonequilibrium spin-polarized current, which plays the role of an effective electrochemical potential on the surface of the TI.

Figure 1

(a) A schematic illustration of the F${}_1$/TI/F${}_2$ junction, where the arrow from F${}_1$ to F${}_2$ shows the applied charge current and the blue arrows represent the direction of the magnetization in F${}_1$ and F${}_2$. (b), (c) The spin polarization $s^y$ for various magnetization configurations with $L/\ell =5$ (solid line), 10 (dashed line), where $L$ is the length between two ferromagnets and $\ell$ is the mean-free path on the surface of TI. The direction of the magnetization F${}_2$ is antiparallel (b) or parallel (c) to that of F${}_1$ [inset (b) or (c)].

Figure 2

The spin polarization, $s_1^y$, for parallel [(a) and (b)] and antiparallel [(c) and (d)] magnetization configurations with $L/\ell =5$. The schematic magnetization configurations in F${}_1$/TI/F${}_2$ junctions are shown in the insets. (e) Magnetoresistance (MR) ratio as a function $L/\ell$. The blue solid and red dashed line represents MR${}_{\downarrow }=\frac{R_{\downarrow \downarrow }-R_{\downarrow \uparrow }}{R_{\downarrow \uparrow }}$ and MR${}_{\uparrow }=\frac{R_{\uparrow \uparrow }-R_{\uparrow \downarrow }}{R_{\uparrow \downarrow }}$, respectively.