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.

Substantial and stable magnetoresistance and spin conductance in phosphorene-based spintronic devices with Co electrodes

Phosphorene-based device with fcc Co(111) electrodes shows excellent spin transport characteristics: large tunnel magnetoresistance ratio and stable spin injection efficiency.

Bias-Dependent Magnetoresistance Device Based on a Magnetically Confined GaAs/AlxGa1– xAs Heterostructure

We apply a bias to a magnetoresistance (MR) device, which is constructed on surface of GaAs/AlxGa1– xAs heterostructure by patterning two asymmetric ferromagnetic stripes. Using improved transfer matrix method and Landauer–Büttiker theory, bias-dependent transmission, conductance and magnetoresistance ratio are calculated numerically. An obvious MR effect appears, because of a significant difference of transmission or conductance between parallel (P) and antiparallel (AP) magnetization configurations. MR ratio can be tuned by adjusting magnitude or direction of applied bias. These interesting features not only propose an alternative way to control MR effect, but also put forward an electrically-tunable MR device for magnetic information storage.

Giant magnetoresistance ratio in a current-perpendicular-to-plane spin valve based on an inverse Heusler alloy Ti2NiAl

A Ti2NiAl inverse Heusler alloy based current-perpendicular-to-plane (CPP) spin valve (SV) with various kinds of atomic terminated interfaces has been designed to explore the potential application of Heusler alloys in spintronics devices. By performing first principles calculations combined with the nonequilibrium Green’s function, it is revealed that spin magnetic moments of interfacial atoms suffer a decrease, and the electronic structure shows that the TiNiB-terminated structure possesses the largest interface spin polarization of ≈55%. Our study on spin-transport properties indicates that the total transmission coefficient at the Fermi level mainly comes from the contribution from the spin up electrons, which are regarded as the majority of the spin electrons. When the two electrodes of the CPP-SV device are in parallel magnetization configuration, the interface containing Ti and Ni atoms possesses a higher spin up transmission coefficient than the interface containing Ti and Al atoms. The device with the TiNiB-terminated interface possesses the largest magnetoresistance ratio of 3.28 × 105, and it has great application potential in spintronics devices.