Large magnetoresistance in a $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{Co}$ magnetic tunnel junction

We demonstrate a large magnetoresistance (MR) in a $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{Co}$ magnetic tunnel junction by means of ab initio transport calculations. A Co electrode turns out to be an excellent spin injector for a $\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2$ barrier. The transmission spectrum, current-voltage characteristics, spin injection efficiency, and magnetoresistance are calculated for the modeled device at various bias voltages in the parallel and antiparallel magnetic configurations. A remarkable change in the transmission spectrum and a subsequent change in total current through the junction have been observed, when the relative magnetic orientations of the electrodes are altered. The huge change in current due to the change in the relative magnetic orientation of the Co electrodes produces a high magnetoresistance up to $1270\%$. The obtained values of the device parameters clearly indicate that a $\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2$ heterostructure would be an excellent compound for highly efficient spin-valve device applications.

Figure 1

Schematic view of the $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{Co}$ device model. Blue, violet, green, and yellow solid spheres represent Co, C, Mo, and S atoms, respectively. The central scattering region is shown within the two dashed lines and the remaining parts are the semi-infinite left and right electrodes.

Figure 2

Spin-resolved transmission spectrum as a function of energy at the equilibrium condition. The black and red lines stand for transmission spectra for the spin-up and spin-down channel, respectively. The Fermi energy is set to zero.

Figure 3

Schematic view of the $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2$ heterostructure. Blue, green, and yellow solid spheres represent Co, Mo, and S atoms, respectively.

Figure 4

The projected density of states for Co (purple) and $\mathrm{Mo}{\mathrm{S}}_2$ (green) in the $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2$ interface. The Fermi energy is set to zero.

Figure 5

Spin-density plot for the $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2$ interface. The red and cyan isosurfaces indicate positive and negative magnetization densities, respectively.

Figure 6

Transmission spectrum of a $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{Co}$ device in the (a) parallel and (b) antiparallel configuration. Black and red curves indicate spin-up and spin-down channels, respectively.

Figure 7

Spin-resolved current-voltage characteristics for a $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{Co}$ device in the (a) parallel and (b) antiparallel configuration. Black and red curves represent current through spin-up and spin-down channels, respectively.

Figure 8

Total current-voltage characteristics of the device in the parallel (green) and antiparallel (blue) configuration.

Figure 9

Magnetoresistance (MR) of the device as a function of applied bias voltage.

Figure 10

Spin injection efficiency (SIE) of the device as a function of applied bias in parallel (green) and antiparallel magnetic configurations of electrodes, respectively.

Figure 11

The $k$-resolved and spin-resolved transmission spectrum along the $k_y$ direction. (a)–(d) represent parallel spin-up, parallel spin-down, antiparallel spin-up, and antiparallel spin-down configurations of a $\mathrm{Co}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{graphene}/\mathrm{Mo}{\mathrm{S}}_2/\mathrm{Co}$ magnetic junction, respectively, at an applied bias 1 V.