RESUMO
Antiferromagnets (AFMs) are some of the most promising candidates for next-generation magnetic memory technology owing to their advantages over conventional ferromagnets (FMs), such as zero stray field and THz-range magnetic resonance frequency. Motivated by the recent synthesis of FeCl2 films with interlayer AFM and intralayer FM couplings, we investigated the magnetic properties of few-layer FeCl2 and the spin-dependent transmissions of graphite/bilayer FeCl2/graphite and Au/n-layer FeCl2/Au magnetic tunnel junctions (MTJs) using first-principles calculations combined with the nonequilibrium Green's function. The interlayer AFM coupling of FeCl2 is certified to be stable and independent of the stacking orders and relative displacement between layers. Furthermore, based on the Au electrode with better conductive performance than the graphite electrode and monolayer 1T-FeCl2 with complete spin polarization, high Curie temperature and large magnetic anisotropic energy, a high tunnel magnetoresistance (TMR) ratio of 2.7 × 103% is achieved in Au/bilayer FeCl2/Au MTJs at zero bias and it increases with different layers of FeCl2 (n = 2-10). These excellent spin transport properties of Au/n-layer FeCl2/Au MTJs based on two-dimensional (2D) AFM barriers with out-of-plane magnetization directions suggest their great potential for application in high-reliability, high-speed and high-density spintronic devices.
RESUMO
Reconfigurable magnetic tunnel diodes have recently been proposed as a promising approach to decrease the base collector leakage currents. However, conventional bulk interfaces usually suffer from strong Fermi level pinning, making it difficult to miniaturize spintronic devices. Fortunately, 2D van der Waals (vdW) systems with ultra-clean interfaces and without dangling bonds can solve this problem. Inspired by the recently discovered novel electronic states of type-II spin gapless semiconductor in 2D VSi2P4 and half-metal in 2D FeCl2, we propose the VSi2P4/FeCl2 vdW heterostructure, and investigate the interface Schottky barrier and the bias-voltage-dependent spin transport properties by using density functional theory and the nonequilibrium Green's function. The most stable vdW interface is determined from the possible twelve interfaces with different stacking sequences and rotation angles. The interface Schottky barrier is beneficial to electrons moving in the spin-down channel due to the Ohmic contact. The heterostructure exhibits a huge rectification ratio (up to 2.9 × 105%) and an excellent spin filtering effect with zero threshold bias voltage, which are explained in terms of the spin-dependent band structure, transmission spectrum and transmission path. These results indicate the promising applications of the VSi2P4/FeCl2 vdW heterostructure as a 2D reconfigurable magnetic diode and a spin filter with miniaturization and low energy consumption.
RESUMO
Two-dimensional (2D) van der Waals (vdW) heterostructures, known as layer-by-layer stacked 2D materials in a precisely chosen sequence, have received more and more attention in spintronics for their ultra-clean interface, unique electronic properties and 2D ferromagnetism. Motivated by the recent synthesis of monolayer 1T-VSe2 with ferromagnetic ordering and a high Curie temperature above room temperature, we investigate the bias-voltage driven spin transport properties of 2D magnetic tunnel junctions (MTJs) based on VSe2 utilizing density functional theory combined with the nonequilibrium Green's function method. In the device 1T-MoSe2/1T-VSe2/2H-WSe2/1T-VSe2/1T-MoSe2, the tunneling magneto-resistance (TMR) is incredibly satisfactory up to 5600%. Based on the analysis of evanescent states, this large TMR is attributed to the spin filter effect at the interface between 1T-VSe2 and 2H-WSe2, which overcomes the low spin polarization of 1T-VSe2. Furthermore, by inserting 2H-MoSe2, the spin filter effect is enhanced with decreasing current and the TMR is drastically improved to 1.7 × 105%. This work highlights the feasibility of 2D vdW heterostructures for ultra-low power spintronic applications by electronic structural engineering.
RESUMO
The complete (100%) spin polarization, zero net magnetic moment and high Curie temperature (605 K) make the recently fabricated half-metallic fully compensated ferrimagnet Mn3Al a promising spintronic material. In order to explore the potential applications in spintronic devices, in this work, we give a theoretical analysis for the Mn3Al/GaAs(0 0 1) heterostructure and the Mn3Al/GaAs/Mn3Al(0 0 1) magnetic tunnel junction. Using the first-principles calculations combined with nonequilibrium Green's function method, we demonstrate from the calculated bias-dependent spin transport properties that the heterostructure exhibits perfect spin filtering effect and spin diode effect, and the magnetic tunnel junction behaves a large tunnel magnetoresistance ratio (up to 10 900%). The physical origins of these versatile spin transport properties are discussed in terms of the half-metallic band structure, the spin-dependent transmission spectra and the band-to-band transmission theory.
RESUMO
Half-metallic ferromagnetic CrO2 has attracted much interest due to its 100% spin polarization and high Curie temperature. CrO2 films have been fabricated on a TiO2 (100) substrate. However, there have been no reports on the spin transport properties of devices based on a CrO2 electrode and TiO2 barrier. In this work, we use first-principles calculations combined with a nonequilibrium Green's function method to investigate the bias-voltage-dependent spin transport properties for the CrO2/TiO2 (100) heterostructure and the CrO2/TiO2/CrO2 (100) magnetic tunnel junction (MTJ). Our results reveal the excellent spin filtering effect and spin diode effect in the heterostructure as well as the high tunnel magnetoresistance ratio (up to 4.48 × 1014%) in the MTJ, which indicate potential spintronic applications. The origins of these perfect spin transport characteristics are discussed in terms of the calculated spin-dependent electrode band structures, the spin-dependent transmission spectra and semiconductor theory.
