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technical paper
Perpendicular Magnetic Tunnel Junctions with Crystalline Anisotropy and Energy efficient Switching of Synthetic Antiferromagnet pMTJs by voltage
In this talk, we first report the roadmap and development of advanced perpendicular magnetic tunnel junctions based on low-damping magnetic materials with crystalline anisotropy that can be scaled down to sub-3-nm diameter with 10 years’ retention time 1. Then, we will present the perpendicular magnetic tunnel junctions (p-MTJs) switched utilizing bipolar electric fields. Traditional voltage-controlled magnetic anisotropy only linearly lowers the energy barrier of ferromagnetic layer via electric field effect and efficiently switches p-MTJs only with a unipolar behavior. Here we propose and demonstrate a bipolar electric field effect switching of 100-nm p-MTJs through voltage-controlled exchange coupling (VCEC) 2. The switching current density, ~1.1×105 A/cm2, is one order of magnitude lower than that of the best-reported spin-transfer torque devices. Theoretical results suggest that electric field induces a ferromagnetic-antiferromagnetic exchange coupling transition and generates a field-like interlayer exchange coupling torque, which cause the bidirectional magnetization switching. We will further report our recent results to switch the p-MTJs using the interplay of SOT and VCEC, which lowers the VCEC switching current density to ~5×103 A/cm23. These results could eliminate the major obstacle in the development of spin memory devices beyond their embedded applications. This technology can be used directly for the future spin-orbit-torque (SOT) MRAM 3 and spin logic devices 4.
References
1 D. Zhang, et al, Phys. Rev. Applied, (2018) vol. 9, 044028
2 D. Zhang, et al, Nano Letters (2022), doi.org/10.1021/acs.nanolett.1c03395
3 B. Zink, et al, Advanced Electronic Materials, (2022), DOI: 10.1002/aelm.202200382
4 M. Mankalale, et al, IEEE Journal on Exploratory Solid-State Computational Devices and Circuits, 3 (2017) 27-36; 10.1109/JXCDC.2017.2690629