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▼ [15p-501-12] Spin-orbit torque memristor, operated by pulsed currents
Keywords:Memristor, Antiferromagnet, Spin-orbit torque
Recently, analogue-like (memristive) spin-orbit torque (SOT) induced magnetization reversal at zero fields was demonstrated in antiferromagnet (AFM)/ferromagnet (FM) systems [1,2]. It was found that AFM plays a triple role: generates SOT, imposes effective in-plane field due to exchange bias (EB) [1] and gives rise to memristive behavior due to domain-to-domain variation of EB [3]. The system is attractive for neuromorphic computing [4]; however, only operation by dc currents was studied so far. Here we show that pulse widths (τp) down to nanoseconds can be used for reliable operation of memristive devices.
We fabricated Hall bar devices with a PtMn/[Co/Ni] stack through sputter-deposition, electron beam lithography and Ar ion milling. To provide EB, fabricated devices were annealed at 300oC for 2 hours in the presence of 1.2 T magnetic field, collinear to the channel.
Hall resistance RHall versus voltage V (RHall-V) curves for τp in the range from 2 s to 1 ns are shown in Fig. 1. Three modes of switching are observed: for τp > 10 ms, RHall-V curves are independent of τp (Fig. 1(a)); for τp < 10 ms, average switching voltage <VSW> increases with decreasing τp; for τp < 500 ns, both <VSW> and the slope of switching region increase (Fig. 1(c)). We find that Joule heating is responsible for this behavior and enables new functionality, such as multiple pulses lengths integration. Reproducibility of short pulse operation is ensured by performing 100 write cycles at τp = 10 ns, 1 µs, 10 ms. The result indicates that reliable separation of RHall states can be achieved for all the studied τp. We conclude that SOT-induced memristive operation can be controlled by pulse length as well as pulse magnitude. The obtained characteristics can pave a way to go beyond digital computing and offer various opportunities such as counters/integrators and artificial synapses in neuromorphic computing.
This work was partly supported by R&D project for ICT Key Technology of MEXT.
[1] S. Fukami, A. K., et al., Nature Mater. 15, 535, (2016). [2] A. van den Brink, et al., Nature Comm. 7, 10854 (2016). [3] A. Kurenkov, et al. (submitted). [4] W. A. Borders, et al., Appl. Phys. Express 10, 013007 (2017).
We fabricated Hall bar devices with a PtMn/[Co/Ni] stack through sputter-deposition, electron beam lithography and Ar ion milling. To provide EB, fabricated devices were annealed at 300oC for 2 hours in the presence of 1.2 T magnetic field, collinear to the channel.
Hall resistance RHall versus voltage V (RHall-V) curves for τp in the range from 2 s to 1 ns are shown in Fig. 1. Three modes of switching are observed: for τp > 10 ms, RHall-V curves are independent of τp (Fig. 1(a)); for τp < 10 ms, average switching voltage <VSW> increases with decreasing τp; for τp < 500 ns, both <VSW> and the slope of switching region increase (Fig. 1(c)). We find that Joule heating is responsible for this behavior and enables new functionality, such as multiple pulses lengths integration. Reproducibility of short pulse operation is ensured by performing 100 write cycles at τp = 10 ns, 1 µs, 10 ms. The result indicates that reliable separation of RHall states can be achieved for all the studied τp. We conclude that SOT-induced memristive operation can be controlled by pulse length as well as pulse magnitude. The obtained characteristics can pave a way to go beyond digital computing and offer various opportunities such as counters/integrators and artificial synapses in neuromorphic computing.
This work was partly supported by R&D project for ICT Key Technology of MEXT.
[1] S. Fukami, A. K., et al., Nature Mater. 15, 535, (2016). [2] A. van den Brink, et al., Nature Comm. 7, 10854 (2016). [3] A. Kurenkov, et al. (submitted). [4] W. A. Borders, et al., Appl. Phys. Express 10, 013007 (2017).