Thickness Dependence of Spin Torque Effect in Fe/MgO/Fe Magnetic Tunnel Junction: Implementation of Divide-and-Conquer with First-Principles Calculation

Bao-Huei Huang^1*, Chia-Chia Chao¹, Yu-Hui Tang¹

¹Department of Physics, National Central University, Taoyuan, Taiwan

* Presenter:Bao-Huei Huang, email:lise811020@gmail.com

The recent epitaxial growth of single-crystal oxides enables the successful fabrication of novel FM/B/FM magnetic heterojunctions, where the central barrier (B) denotes complex transition metal oxides that exhibit high variety of physical phenomena. Many of these spintronics technologies rely on the current-driven spin torque effects. From computational point of view, their magnetoelectric and magnetotransport properties are usually oversimplified by energy parameters used in the tight-binding model, due to the self-consistent difficulties in first-principles calculation with complex interfacial charge transfer and large size of device.

To resolve these computational issues, in this study, we implement a divide-and-conquer method within the first-principles framework in our newly developed JunPy package [1] to solve the Hamiltonian of Fe/MgO/Fe MTJ with large amount of Fe layers, efficiently but without losing accuracy. Our results reveal the oscillatory decay of layer-resolved and cumulative spin torques for the Fe electrode with finite thickness, and suggest that the Fe layer thickness should no larger than 2 nm to preserve the current-driven magnetization switching process [2]. We believe our JunPy-DC calculation may efficiently resolve current self-consistent difficulties in noncollinear spin torque effects for novel and large spintronic devices, e.g., multiple capping layers structure, spin-dependent quantum well resonant tunneling and antiferromagnetic tunnel junctions.

[1] https://labstt.phy.ncu.edu.tw/junpy
[2] B.-H. Huang, C.-C. Chao, Y.-H. Tang, “Thickness Dependence of Spin Torque Effect in Fe/MgO/Fe Magnetic Tunnel Junction: Implementation of Divide-and-Conquer with First-Principles Calculation”, manuscript in submission

Keywords: Spin-transfer torque, First-Principles Calculation, Spin current, Magnetic Tunnel Junction