Magnetic tunneling junctions based on 2D CrI3 and CrBr3: spin filtering effects and high tunnel magnetoresistance via energy band difference

Recently, the study on two-dimensional materials expands to the field of spintronics. The intrinsically ferromagnetic van der Waals materials such as CrI3 and CrBr3 receive much attention due to nearly 100% spin polarization and good stability, resulting in excellent performance in magnetic tunnel junctions. In this work, we design the magnetic tunnel junctions of Cu/CrI3/Cu and Cu/CrBr3/Cu with the electrodes of Cu(111) and the tunneling barrier of 4-monolayer CrI3 or CrBr3. Our first-principle calculations combined with nonequilibrium Green’s function method indicate that the CrBr3-based MTJ has a larger maximum tunneling magnetoresistance ratio than the CrI3-based MTJ. In a wide bias voltage range, the CrI3-based MTJ can maintain high spin filtering performance, while that of the CrBr3-based MTJ degrades sharply as the bias voltage increases. It is noted that negative differential resistance effect is observed in the CrBr3-based MTJ. The differences of spin transport properties between the CrI3-based MTJ and the CrBr3-based MTJ are clarified in terms of the inside device physics, including the spin-dependent projected density of states, band structures, Bloch states, and the electron density difference. This work provides some physical insights for the design of 2D van der Waals MTJ.