Simulation Study on Understanding the Spin Transport in MgO Adsorbed Graphene Based Magnetic Tunnel Junction

First principles calculations of spin-dependent electronic transport properties of magnetic tunnel junction (MTJ) consisting of MgO adsorbed graphene nanosheet sandwiched between two CrO2 half-metallic ferromagnetic (HMF) electrodes is reported. MgO adsorption on graphene opens bandgap in graphene nanosheet which makes it more suitable for use as a tunnel barrier in MTJs. It was found that MgO adsorption suppresses transmission probabilities for spin-down channel in case of parallel configuration (PC) and also suppresses transmission in antiparallel configuration (APC) for both spin-up and spin-down channel. Tunnel magneto-resistance (TMR) of 100% is obtained at all bias voltages in MgO adsorbed graphene-based MTJ which is higher than that reported in pristine graphene-based MTJ. HMF electrodes were found suitable to achieve perfect spin filtration effect and high TMR. I–V characteristics for both parallel and antiparallel magnetization states of junction are calculated. High TMR suggests its usefulness in spin valves and other spintronics-based applications.

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Effect of inserted Cu layer on CoFe/Cu/MgO/CoFe magnetic tunnel junction

International Journal of Modern Physics B ◽

10.1142/s0217979215501714 ◽

2015 ◽

Vol 29 (24) ◽

pp. 1550171

Author(s):

Baoan Bian ◽

Bing Chu ◽

Zhuomao Zhu ◽

Yapeng Zheng

Keyword(s):

Bias Voltage ◽

Density Functional ◽

Magnetic Tunnel Junction ◽

Oscillation Period ◽

Tunneling Magnetoresistance ◽

Tunnel Barrier ◽

First Principles Calculations ◽

Zero Bias ◽

Functional Theory ◽

Quantum Well State

In this paper, we carried out first-principles calculations based on density functional theory and nonequilibrium Green’s function to investigate the tunneling magnetoresistance effect in CoFe/Cu/MgO/CoFe magnetic tunnel junctions. Insertion of a nonmagnetic Cu layer between the tunnel barrier and the electrode is shown to result in the inverse and oscillation of the tunneling magnetoresistance as a function of the Cu layer at different bias voltage. The inverse phenomenon is discussed in terms of the conductance and the tunneling probability of electron at zero bias voltage. We suggest that the oscillation of tunneling magnetoresistance results from quantum well state formed in nonmagnetic Cu layer which can bring about the multiple scattering of tunneling electrons due to influence of the bias voltage on the oscillation period of the tunneling magnetoresistance.

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Novel Stack Structure of Magnetic Tunnel Junction with MgO Tunnel Barrier Prepared by Oxidation Methods: Preferred Grain Growth Promotion Seed Layers and Bi-layered Pinned Layer

Japanese Journal of Applied Physics ◽

10.1143/jjap.48.120214 ◽

2009 ◽

Vol 48 (12) ◽

pp. 120214 ◽

Cited By ~ 21

Author(s):

Young-suk Choi ◽

Hiroshi Tsunematsu ◽

Shinji Yamagata ◽

Hiroki Okuyama ◽

Yoshinori Nagamine ◽

...

Keyword(s):

Grain Growth ◽

Tunnel Junction ◽

Growth Promotion ◽

Magnetic Tunnel Junction ◽

Tunnel Barrier ◽

Seed Layers

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Molecular coupling competing with defects within insulator of the magnetic tunnel junction-based molecular spintronics devices

Scientific Reports ◽

10.1038/s41598-021-96477-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Pawan Tyagi ◽

Hayden Brown ◽

Andrew Grizzle ◽

Christopher D’Angelo ◽

Bishnu R. Dahal

Keyword(s):

Tunnel Junction ◽

Magnetic Tunnel Junction ◽

Tunnel Barrier ◽

Molecular Device ◽

Molecular Spintronics ◽

Ferromagnetic Electrodes ◽

Covalently Bonded ◽

Wide Range ◽

Device Properties ◽

Theoretical Simulations

AbstractNearly 70 years old dream of incorporating molecule as the device element is still challenged by competing defects in almost every experimentally tested molecular device approach. This paper focuses on the magnetic tunnel junction (MTJ) based molecular spintronics device (MTJMSD) method. An MTJMSD utilizes a tunnel barrier to ensure a robust and mass-producible physical gap between two ferromagnetic electrodes. MTJMSD approach may benefit from MTJ's industrial practices; however, the MTJMSD approach still needs to overcome additional challenges arising from the inclusion of magnetic molecules in conjunction with competing defects. Molecular device channels are covalently bonded between two ferromagnets across the insulating barrier. An insulating barrier may possess a variety of potential defects arising during the fabrication or operational phase. This paper describes an experimental and theoretical study of molecular coupling between ferromagnets in the presence of the competing coupling via an insulating tunnel barrier. We discuss the experimental observations of hillocks and pinhole-type defects producing inter-layer coupling that compete with molecular device elements. We performed theoretical simulations to encompass a wide range of competition between molecules and defects. Monte Carlo Simulation (MCS) was used for investigating the defect-induced inter-layer coupling on MTJMSD. Our research may help understand and design molecular spintronics devices utilizing various insulating spacers such as aluminum oxide (AlOx) and magnesium oxide (MgO) on a wide range of metal electrodes. This paper intends to provide practical insights for researchers intending to investigate the molecular device properties via the MTJMSD approach and do not have a background in magnetic tunnel junction fabrication.

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