Dynamics-based neuromorphic properties of spintronics devices

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15428
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29010:Applied physical properties-related
• Research Institution: Tohoku University
• Principal Investigator: Kurenkov Aleksandr 東北大学, 先端スピントロニクス研究開発センター, 学術研究員 (80830645)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: neuromorphic computing / synapse / neuron / spintronics / exchange bias / antiferromagnet / ferromagnet

Outline of Final Research Achievements

We have clarified the microscopic mechanism behind spin-orbit torque switching in ferromagnet/antiferromagnet (FM/AFM) stacks. It was found that exchange bias (EB) at the FM/AFM interface varies throughout the system and causes non-binary behavior. This variation happens at a fine scale of the stack grain size i.e. ~ 15 nm. Within a grain, the FM/AFM interface can be assumed to be monocrystalline and it can give EB as large as hundreds of mT. Much weaker EB of ~20-40 mT, previously measured at the FM domain level (~ 200 nm in effective diameter) can be explained by averaging effects. EB in each site is determined by crystallographic orientation of the grain and the quality of the FM/AFM interface, which leads to a wide dispersion of values in polycrystalline non-epitaxial systems.

Free Research Field

Neuromorphic computing with spintronics

Academic Significance and Societal Importance of the Research Achievements

The new picture of EB in polycrystalline systems, confirmed experimentally and with simulations, is crucial for understanding and engineering of EB both for fundamental studies and neuromorphic applications.