Magnetic tunnel junctions and magnetic logic circuits driven by spin-orbit torques

Pietro Gambardella,

Department of Materials, ETH Zurich, Switzerland

Current-induced spin-orbit torques (SOTs) enable the switching of magnetic tunnel junctions (MTJs) in nonvolatile magnetic random access memories as well as the all-electrical operation of magnetic logic circuits based on domain wall manipulation. In this talk, I will present time-resolved measurements of magnetization reversal driven by SOTs in 3-terminal MTJ devices and discuss how the combination of SOT, spin transfer torque, and voltage control of magnetic anisotropy leads to reproducible sub-ns magnetization reversal with a very narrow spread of the switching time distributions [1]. Further, I will show how SOTs and the chiral coupling between neighbouring magnetic domains induced by the interfacial Dzyaloshinskii–Moriya interaction [2] allow for realizing an electrically-driven domain-wall inverter. Starting from this basic building block, it is possible to fabricate reconfigurable NAND and NOR logic gates, and therefore a complete family of logic gates, which perform operations with current-induced domain-wall motion [3]. Opportunities for scalable all-electric magnetic memories and memory-in-logic applications will be discussed.

PDF file of the talk available here

References

[1] Single-shot dynamics of spin-orbit torque and spin transfer torque switching in 3-terminal magnetic tunnel junctions, E. Grimaldi, V. Krizakova, G. Sala, F. Yasin, S. Couet, G. S. Kar, K. Garello and P Gambardella, Nat. Nanotech. 15, 111 (2020).
[2] Chirally Coupled Nanomagnets, Z. Luo, T. Phuong Dao, A. Hrabec, J. Vijayakumar, A. Kleibert, M. Baumgartner, E. Kirk, J. Cui, T. Savchenko, G. Krishnaswamy, L. J. Heyderman, and P. Gambardella, Science 363, 1435 (2019).
[3] Current-driven magnetic domain-wall logic, Z. Luo, A. Hrabec, T. P. Dao, G. Sala, S. Finizio, J. Feng, S. Mayr, J. Raabe, P. Gambardella, L. J. Heyderman, Nature 579, 214 (2020).

Figure 1. a, Scanning electron microscope image of a 3-terminal magnetic tunnel junction device with injection electrodes for spin-orbit torque (SOT) and spin transfer torque (STT) switching. b, Detail of the magnetic tunnel junction pillar and W current line. c, Electrical setup for the time-resolved measurements of the tunneling magnetoresistance during SOT and/or STT switching. d, Examples of ten different single-shot switching events induced by spin-orbit torques. Adapted from [1].