Layer-Dependent Giant Magnetoresistance in Two-Dimensional ${\mathrm{Cr}\mathrm{PS}}_4$ Magnetic Tunnel Junctions

Antiferromagnetism within the two-dimensional (2D) family offers a platform for spintronics. The emergent 2D semiconductor ${\mathrm{Cr}\mathrm{PS}}_4$ is proved to be composed of ferromagnetic layers with antiferromagnetic coupling along the stacking direction in the experiment. By using the first-principles quantum-transport simulation, we evaluate the spin-resolved transport in the magnetic tunnel junction built by the 2D ${\mathrm{Cr}\mathrm{PS}}_4$ tunnel barrier with large thickness ranges. We find the magnetoresistance generally increases with the number of tunnel layers from 140% (three layers) to a surprising 370 000% (10 layers). An odd-even oscillation magnetoresistance behavior exists in few layers due to the electrode option. Our results will inspire further experimental verification and provide vital insights for 2D spintronics design.

Figure 1

Lattice and electronic structures of ${\mathrm{Cr}\mathrm{PS}}_4$. The top (a) and side (b) view of bulk ${\mathrm{Cr}\mathrm{PS}}_4$. The arrows represent the magnetic moments in each layer. The red dash parallelogram is the primitive lattice. (c)–(e) Spin-dependent band structures for bilayer, 3-layer, and bulk ${\mathrm{Cr}\mathrm{PS}}_4$ in the AFM and FM states. A 1 × 1 × 2 supercell is applied to calculate the bulk band structures.

Figure 2

(a) Device model of the $\mathrm{Au}/$n-layer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ magnetic tunnel junction. The conductance (b) and spin polarization (c) in the FM and AFM states, and TMR in a log scale (d) as a function of the ${\mathrm{Cr}\mathrm{PS}}_4$ layer number n.

Figure 3

(a) Device model of the graphite/2D ${\mathrm{Cr}\mathrm{PS}}_4/$graphite MTJ. (b) Comparison of layer-dependent tunneling magnetoresistance of the graphite/n-layer ${\mathrm{Cr}\mathrm{PS}}_4/$graphite and the $\mathrm{Au}/$n-layer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ (n is from 2 to 7) MTJs.

Figure 4

Spin-resolved projected LDOS of the $\mathrm{Au}/$bilayer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ magnetic tunnel junction (a)–(d) and the graphite//bilayer ${\mathrm{Cr}\mathrm{PS}}_4/$graphite magnetic tunnel junction (e)–(h).

Figure 5

Spin-resolved projected LDOS of the $\mathrm{Au}$/3-layer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ magnetic tunnel junction (a)–(d) and the graphite//3-layer ${\mathrm{Cr}\mathrm{PS}}_4/$graphite magnetic tunnel junction (e)–(h).

Figure 6

Spin-resolved projected LDOS of the $\mathrm{Au}$/4-layer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ magnetic tunnel junction (a)–(d) and the graphite//4-layer ${\mathrm{Cr}\mathrm{PS}}_4/$graphite magnetic tunnel junction (e)–(h).

Figure 7

Spin-resolved projected LDOS of the $\mathrm{Au}$/7-layer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ magnetic tunnel junction for the FM [(a) and (b)] and AFM [(c) and (d)] states. The number marked in (a) indicates the different ${\mathrm{Cr}\mathrm{PS}}_4$ layer. The Fermi level is zero. The black lines are the boundary of the electrode and tunnel region. The green lines are the spin-dependent potential barrier profile. The LDOS are in the log scale. The barrier heights are labeled.

Figure 8

k_∥-resolved transmission coefficients across the $\mathrm{Au}/$n-layer ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Au}$ (n is from 3 to 10) magnetic tunnel junction in the Brillouin zone for the FM and AFM state calculated at the Fermi level.

Figure 9

Spin-resolved band structures of 4 to 10 layers CrPS₄ in the AFM and FM states.

Figure 10

Lattice structure of the Au/3-layer CrPS₄/Au heterostructure before and after geometry optimization.