| 研究実績の概要 |
In FY2020 we have clarified the microscopic mechanism behind magnetic domains formation during spin-orbit torque switching in ferromagnet/antiferromagnet (FM/AFM) stacks. The key finding is that variation of exchange bias (EB), which causes non-binary behavior happens at a fine scale of the stack grain size i.e. ~ 15 nm. At this scale, exchange interaction at the FM/AFM interface acts in monocrystalline environment and thus can be 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) is, in fact, averaged over multiple grains. The new picture of tiny pinning sites with strongly varied potential at FM/AFM interface is crucial for understanding of EB and engineering of control pulses for neuromorphic applications.
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