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VIDEO DOI: https://doi.org/10.48448/j2d2-r572

technical paper

MMM 2022

November 07, 2022

Minneapolis, United States

Stochastic Magnetic Actuated Random Transducer Devices based on Perpendicular Magnetic Tunnel Junctions

Neuromorphic systems are of great interest for modeling and solving complex problems, offering an alternative to conventional deterministic computers1. They generally aim to emulate the functionality and structure of the human brain and thus require many independent true random noise signal sources. In recent years, the stochasticity of spin-transfer-torque switching of magnetic tunnel junctions (MTJs) has gained interest for such applications. Focusing on in-plane MTJs with low energy barriers, the devices investigated thus far have fast thermally driven random fluctuations2,3. However, they are highly susceptible to small changes in temperature and device parameters. Here we show the room-temperature operation of medium energy barrier (Δ=394) perpendicularly magnetized MTJs (pMTJs) in the ballistic switching limit (ns duration pulses) and discuss why their operation is much less sensitive to temperature and material parameters. In the ballistic limit the resulting junction state is random mainly because of the thermal distribution of the initial magnetization state. We denote this a stochastic magnetic actuated random transducer (SMART) device because the pulse activates the junction to generate a random bit stream, much like a coin flip. In fact, we analyze the stochastic nature of our SMART devices by comparing their statistics to that expected of Bernoulli trials (see Figs.1 and 2). We also test our bit stream with the NIST statistical test suite for random number generators which investigates their suitability for cryptography. We find that by whitening the bit stream with only one XOR operation, we pass all NIST tests. Our results demonstrate that medium energy barrier pMTJs are very promising candidates for true random number generation due to their easily controllable characteristics, while being robust towards environmental changes and material parameter variations.

References 1Schuman, C. D. et al., arXiv:1705.06963. 2Vodenicarevic, D. et al., Physical Review Applied Vol. 8, 054045 (2017). 3Safranski, C. et al., Nano Letters Vol. 21, 2040–2045 (2021). 4Rehm, L. et al., Physical Review Applied Vol. 15, 034088 (2021).


Transcript English (automatic)

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