Bipolar Electric-Switching of Perpendicular Magnetic Tunnel Junctions with through Voltage-controlled Exchange Coupling (VCEC)
Presenter: Prof. Jian-Ping Wang, University of Minnesota
Abstract: Perpendicular magnetic tunnel junctions (p-MTJs) that can be switched utilizing a bipolar electric field (E-field) have potential for extensive applications in energy efficient memory and logic systems. E-field effects relying on voltage-controlled magnetic anisotropy can lower the energy barrier of ferromagnetic (FM) layers for magnetization switching. However, this effect only works in a unipolar E-field, and a bias magnetic field or spin-polarized current is required for bidirectional magnetization reversal. On the other hand, the E-field is proposed to be able to tune the sign of the interlayer exchange coupling between two FM layers via modulation of the spin reflectivity at the interfaces. This suggests possibilities for bipolar E-field controlled bidirectional magnetization switching, which has not been realized experimentally. Here we demonstrate bipolar E-field bidirectional switching of sub-100 nanometer p-MTJs without bias magnetic field through a voltage-controlled exchange coupling (VCEC). A low critical current density ~1×10^5 A/cm2 is obtained, which is one order of magnitude lower than that of the best-reported STT devices. Theory suggests that the torque generated from the interlayer exchange coupling in p-MTJs contributes to the bipolar magnetization switching. Furthermore, a preliminary CMOS-based benchmarking calculation estimates that VCEC-MTJs dissipate more than an order of magnitude lower energy per write operation compared to spin-transfer-torque magnetoresistive random access memory (STT-MRAM) and are 5.5X denser than spin-orbit torque (SOT) MRAM if implemented at the 7 nm technology node. These results could eliminate the major obstacle in the development of MRAM for applications beyond its current use only for embedded memory.
1. D. L. Zhang, et al., L10 FePd synthetic antiferromagnet through an fcc Ru spacer utilized for perpendicular magnetic tunnel junctions, Phys. Rev. Applied 9, 044028 (2018).
2. D. L. Zhang, et al., Bidirectional switching of perpendicular magnetic tunnel junctions through voltage-controlled exchange coupling, submitted, 2019, arXiv preprint arXiv:1912.10289
Jian-Ping Wang is the Robert F. Hartmann Chair and a Distinguished McKnight University Professor of Electrical and Computer Engineering, and a member of the graduate faculty in Physics, Chemical Engineering and Materials Science and Biomedical Engineering at the University of Minnesota. He received the information storage industry consortium (INSIC) technical award in 2006 for his pioneering work in exchange coupled composite magnetic media and the outstanding professor award for his contribution to undergraduate teaching in 2010. He is also the recipient of 2019 SRC Technical Excellence Award for his innovations and discoveries in nanomagnetics and novel materials that accelerated the production of magnetic random-access memories. He has authored and co-authored more than 300 publications in peer-reviewed top journals and conference proceedings and holds 55 patents. He is an IEEE fellow.
This meeting is only available to the JUMP research community, such as Principal Investigators, Postdoc researchers, Students, and Industry/Government liaisons.