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

Abstract

Recently, the study of two-dimensional materials has expanded to the field of spintronics. Intrinsically ferromagnetic van der Waals materials such as CrI3 and CrBr3 have received much attention due to their nearly spin polarization and good stability, resulting in excellent performance in magnetic tunnel junctions. In this work, we design magnetic tunnel junctions (MTJs) of Cu/CrI3/Cu and Cu/CrBr3/Cu with electrodes of Cu(111) and a tunneling barrier of four-monolayer CrI3 or CrBr3. Our first-principle calculations combined with non-equilibrium 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 a negative differential resistance effect is observed in the CrBr3-based MTJ. The differences in spin transport properties between the CrI3-based MTJ and the CrBr3-based MTJ are clarified in terms of the physics inside the device, including the spin-dependent 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 MTJs.