Ultrathin Scattering Spin Filter and Magnetic Tunnel Junction Implemented by Ferromagnetic 2D van der Waals Material

ACS Appl. Mater. Interfaces

Zhao

2020

Two-dimensional (2D) van der Waals (vdW) heterostructures have opened new avenues for spintronic applications with novel properties. Here, by density functional theory calculations, we investigated the spin-dependent transport in vdW magnetic tunnel junctions (MTJs) composed of 1T-CrTe 2 ferromagnetic electrodes. Meanwhile, graphene and h-BN are employed as tunnel barriers. It has been found that the tunneling magnetoresistance (TMR) effects of two types of vdW MTJs present analogous trends: thicknesses of barriers have a great influence on the TMR ratios, which reach up to the maximum when barriers increase to five monolayers. However, despite the similarity, the graphene−barrier junction is more promising for optimization. Through observing the energy-resolved transmission spectra of vdW MTJs, we noticed that TMR ratios of graphene−barrier junctions are tunable and could be enhanced through tuning the position of Fermi energy. Therefore, we successfully realized the TMR optimization by substitutional doping. When substituting one carbon atom with one boron atom in the graphene barrier, TMR ratios are drastically improved, and a TMR ratio as high as 6962% could be obtained in the doped seven-monolayer−barrier junction. Our results pave the way for vdW MTJ applications in spintronics.

Section: ■ Introductionmentioning

confidence: 99%

Tunable Tunneling Magnetoresistance in van der Waals Magnetic Tunnel Junctions with 1T-CrTe₂ Electrodes

Zhou

ACS Appl. Mater. Interfaces

Zhao

2020

“…The MTJ consists of an insulator sandwiched between two magnetic electrodes. Previous investigations show that many exceptional spin-related phenomena such as spin filtering, tunnel magnetoresistance (TMR), and the Kondo effect, have been discovered in these junctions. − TMR is an important physical phenomenon that has a tremendous economic impact on magnetic information storage, including magnetoresistive random access memory (MRAM), microwave generators, radiofrequency sensors, and neuromorphic computing networks. Since the first detection of TMR in the FM/Al 2 O 3 /FM junction at room temperature, , a great deal of efforts has been made to this issue.…”

Section: Introductionmentioning

confidence: 99%

Perfect Spin Filtering Effect on Fe₃GeTe₂-Based Van der Waals Magnetic Tunnel Junctions

et al. 2020

J. Phys. Chem. C

Conventional magnetic tunnel junctions (MTJs) face many issues in experiments and cannot meet a human’s urgent demand. Thus, van der Waals (vdW) MTJs increase in response to the proper time and conditions. By employing the combination of density functional theory (DFT) with the nonequilibrium Green’s function (NEGF) methods, Fe3GeTe2|InSe|Fe3GeTe2 vdW MTJs is proposed for the first time. Fe3GeTe2 has proven to be an excellent electrode for vdW MTJ applications, which shows a nature metallic FM characteristic with a high Curie temperature. Furthermore, semiconductor InSe with high electron mobility, a quantum Hall effect, and high stability is selected to be used as a tunneling barrier without lattice mismatching. Our designed MTJs show equal ability as a spin up and spin down filter. One can obtain a different spin-directional current only by changing the bias polarity without very high purity addition. Furthermore, a high tunnel magnetoresistance (TMR) ratio can reach up to ∼700%. The physical mechanisms behind this interesting phenomenon are given by analyzing k ||-resolved transmission spectra and a complex band structure. Our results would provide theoretical foundation for designing two-dimensional spintronic logic, ultrafast magnetodynamics devices and information storage for new generation computer devices.

“…A similar theoretical investigation of a 2D spin filter and spin-filter MTJs consisting of atomically thin Fe3GeTe2 was also reported. 144 The models and the main data are shown in Figs. 6 (a-d).…”

Section: (E-g))mentioning

confidence: 99%

Recent progress and challenges in magnetic tunnel junctions with 2D materials for spintronic applications

Applied Physics Reviews

Zhou

et al. 2021

As Moore's law is gradually losing its effectiveness, developing alternative high-speed and low-energy-consuming information technology with post-silicon advanced materials is urgently needed. The successful application of tunneling magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) has given rise to a tremendous economic impact on magnetic informatics, including MRAM, radio-frequency sensors, microwave generators and neuromorphic computing networks. The emergence of twodimensional (2D) materials brings opportunities for MTJs based on 2D materials which have many attractive characters and advantages. Especially, the recently discovered intrinsic 2D ferromagnetic materials with high spin-polarization hold the promise for next-generation nanoscale MTJs. With the development of advanced 2D materials, many efforts on MTJs with 2D materials have been made both theoretically and experimentally. Various 2D materials, such as semi-metallic graphene, insulating h-BN, semiconducting MoS2, magnetic semiconducting CrI3, magnetic metallic Fe3GeTe2 and some other recently emerged 2D materials are discussed as the electrodes and/or central scattering materials of MTJs in this review. We discuss the fundamental and main issues facing MTJs, and review the current progress made with 2D MTJs, briefly comment on work with some specific 2D materials, and highlight how they address the current challenges in MTJs, and finally offer an outlook and perspective of 2D MTJs.