Abstract
Spin-based computing schemes could enable new functionalities beyond those of charge-based approaches1,2,3,4,5,6. Examples include nanomagnetic logic, where information can be processed using dipole coupled nanomagnets7,8,9,10,11,12,13,14, as demonstrated by multi-bit computing gates8,13. One fundamental benefit of using magnets is the possibility of a significant reduction in the energy per bit compared with conventional transistors1,8,14,15. However, so far, practical implementations of nanomagnetic logic have been limited by the necessity to apply a magnetic field for clocking8,11. Although the energy associated with magnetic switching itself could be very small, the energy necessary to generate the magnetic field renders the overall logic scheme uncompetitive when compared with complementary metal–oxide–semiconductor (CMOS) counterparts. Here, we demonstrate a nanomagnetic logic scheme at room temperature where the necessity for using a magnetic field clock can be completely removed by using spin–orbit torques16,17,18,19,20,21,22. We construct a chain of three perpendicularly polarized CoFeB nanomagnets on top of a tantalum wire and show that an unpolarized current flowing through the wire can ‘clock’ the perpendicular magnetization to a metastable state. An input magnet can then drive the nanomagnetic chain deterministically to one of two dipole-coupled states, ‘2 up 1 down’ or ‘2 down 1 up’, depending on its own polarization. Thus, information can flow along the chain, dictated by the input magnet and clocked solely by a charge current in tantalum, without any magnetic field. A three to four order of magnitude reduction in energy dissipation is expected for our scheme when compared with state-of-the-art nanomagnetic logic.
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Acknowledgements
The authors thank E. Chen and X. Tang of Grandis Corporation for help with material preparation, and D. Nikonov and J. Bokor for valuable discussions. This work was supported in part by the Defense Advance Research Projects Agency Non-Volatile Logic Program, the National Science Foundation Center for Energy Efficient Electronics Science Centre at Berkeley, and the Semiconductor Research Corporation Western Institute of Nanoelectronics centre.
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L.Y. fabricated the devices. D.B. and L.Y. performed measurements. S.S. conceived and supervised the overall project. All authors discussed and analysed data and participated in writing the manuscript.
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Bhowmik, D., You, L. & Salahuddin, S. Spin Hall effect clocking of nanomagnetic logic without a magnetic field. Nature Nanotech 9, 59–63 (2014). https://doi.org/10.1038/nnano.2013.241
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DOI: https://doi.org/10.1038/nnano.2013.241
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