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About Overview Organization & Management Strategy Open Positions Movie Library Access Research Structure Researchers & Laboratories Research Areas Three Advanced Target Projects Collaboration Achievements Press Releases Media & Award AIMResearch Publications Topics News Seminars & Symposium International Satellites International Partner Institutions Inter-Faculty Exchange Agreements Researcher Exchange Programs Support Support Systems For International Researchers (IAC) For Visitors Researchers for Visitors for Researchers for Enterprise Access AIMR Fund Japanese Research Highlights Spintronics: Entropy probes stochastic relaxation times of nanomagnets 01/22/2024 Uncovering design guidelines for probabilistic computing devices Dr. Kanai, the corresponding author of the article As neuromorphic applications such as machine learning and artificial intelligence continue to expand, progress in p-bit research1, 2 promises to use probabilistic computing to meet their escalating energy and efficiency demands. To this end, a recent approach that directly contributed to the p-bit hardware implementation focused on the switching volatility of stochastic magnetic tunnel junctions (MTJs). An example of this is a 2021 article by Kanai et al. from AIMR, who investigated which MTJ features control the relaxation time between the “1” and “0” states of stochastic nanomagnets3. “Our idea was to model the stochasticity of magnetic systems using entropy,” explains Kanai. “At the time of this work, this method had never been used to study magnetization dynamics.” Deriving a universal equation governing the entropy in magnetization dynamics, the research team discovered that the entropy rapidly increases in nanomagnets with an in-plane magnetic easy axis and larger magnitudes of perpendicular magnetic anisotropy, suggesting the in-plane easy axis to be conducive to shorter relaxation times. These theoretical results later enabled the team to fabricate stochastic MTJs with relaxation times in the nanosecond range—100,000 time faster than the contemporaneous standard MTJs4. “Our theoretical work on relaxation time did not only help us realize faster MTJs,” says Kanai. “It also provided design information on how to tailor the input-output properties and robustness against external magnetic fields of these devices5, 6.” (Author: Patrick Han) References Camsari, K.Y., Faria R., Sutton, B.M., & Datta, S. Stochastic p-bits for invertible logic Phys. Rev. X 7, 031014 (2017). | article Borders, W.A., Pervaiz, A.Z., Fukami S., Camsari, K.Y., Ohno, H. & Datta, S. Integer factorization using stochastic magnetic tunnel junctions Nature 573, 390 (2019). | article Kanai, S., Hayakawa, K., Ohno, H. & Fukami, S. Theory of relaxation time of stochastic nanomagnets Physical Review B 103, 094423 (2021). | article Hayakawa, K., Kanai, S., Funatsu, T., Igarashi, J., Jinnai, B., Borders, W.A., Ohno, H. & Fukami, S. Nanosecond random telegraph noise in in-plane magnetic tunnel junctions Physical Review Letters 126, 117202 (2021). | article Kobayashi, K., Borders, W. A., Kanai, S., Hayakawa, K., Ohno, H. & Fukami, S. Sigmoidal curves of stochastic magnetic tunnel junctions with perpendicular easy axis Applied Physics Letters 119, 132406(1)-(5) (2021). | article Funatsu, T., Kanai, S., Ieda, J., Fukami, S., & Ohno, H. Local bifurcation with spin-transfer torque in superparamagnetic tunnel junctions Nature Communications 13, 4079(1)-(8) (2022). | article This research highlight has been approved by the authors of the original article and all information and data contained within has been provided by said authors. keywords spintronics entropy magnetic tunnel junctions stochastic relaxation times nanomagnets probabilistic computing Tweet more Research Highlights Achievements Press Releases 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 Media & Award 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 AIMResearch About AIMResearch Research Highlights 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 In the Spotlight 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 Email Alert Sign up Publications Headlines 2024/05/31 Dr. Yi Shuang selected to receive a Hara... 2024/05/22 Machine Learning Accelerates Discovery o... 2024/05/16 New Data-Driven Model Rapidly Predicts D... 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