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▼ [11a-M101-9] Observation of memristive domain patterns during spin-orbit torque switching in antiferromagnet/ferromagnet heterostructures
Keywords:antiferromagnet, memristor, XMCD
Efficient field-free spin-orbit torque (SOT) magnetization switching has been achieved by use of antiferromagnet (AFM)/ferromagnet (FM) structures [1]. In addition, use of the AFM in them leads to formation of reproducible analogue-like (or “memristive”) switching with multiple nonvolatile states, allowing applications in neural networks [2]. Additional electrical measurements suggested that the memristivity originates from separate switching of binary domains of 200 nm scale [3], which is nonsimultaneous due to exchange bias (EB) variation. The described picture significantly differs from the conventional SOT switching in nonmagnet (NM)/FM heterostructures.
Here we use X-ray magnetic circular dichroism, an insightful tool for SOT switching studies [4], and couple it to photoemission electron microscopy to image ferromagnetic domains of an AFM/FM heterostructure in its intermediate memristive states in the sputter-deposited stacks of Ta/ Pt/ PtMn/ [Co/Ni]2/ Co/ MgO/ Ru. The experiment revealed memristive domain patterns with feature size of the order of 100 nm which are distinctly different from NM/FM cases. We found that domains reproduce themselves in repetitive switching sequences and do not evolve between the applied pulses. Trains of pulses induced gradual switching by domain expansion. This is the first imagining of field-free SOT switching and it clarifies the way for achieving memristors and binary AFM/FM cells of desired properties.
A portion of this work was supported by the ImPACT Program of CSTI and JST-OPERA and Grant 200020_172775 of Swiss National Science Foundation.
[1] S. Fukami, C. Zhang, S. DuttaGupta, A. Kurenkov and H. Ohno, Nat. Mater. 15, 535 (2016).
[2] W. A. Borders et al., Appl. Phys. Express 10, 013007 (2017).
[3] A. Kurenkov, C. Zhang, S. DuttaGupta, S. Fukami and H. Ohno, Appl. Phys. Lett. 110, 092410 (2017).
[4] M. Baumgartner et al., Nat. Nanotech. 12, 980 (2017).
Here we use X-ray magnetic circular dichroism, an insightful tool for SOT switching studies [4], and couple it to photoemission electron microscopy to image ferromagnetic domains of an AFM/FM heterostructure in its intermediate memristive states in the sputter-deposited stacks of Ta/ Pt/ PtMn/ [Co/Ni]2/ Co/ MgO/ Ru. The experiment revealed memristive domain patterns with feature size of the order of 100 nm which are distinctly different from NM/FM cases. We found that domains reproduce themselves in repetitive switching sequences and do not evolve between the applied pulses. Trains of pulses induced gradual switching by domain expansion. This is the first imagining of field-free SOT switching and it clarifies the way for achieving memristors and binary AFM/FM cells of desired properties.
A portion of this work was supported by the ImPACT Program of CSTI and JST-OPERA and Grant 200020_172775 of Swiss National Science Foundation.
[1] S. Fukami, C. Zhang, S. DuttaGupta, A. Kurenkov and H. Ohno, Nat. Mater. 15, 535 (2016).
[2] W. A. Borders et al., Appl. Phys. Express 10, 013007 (2017).
[3] A. Kurenkov, C. Zhang, S. DuttaGupta, S. Fukami and H. Ohno, Appl. Phys. Lett. 110, 092410 (2017).
[4] M. Baumgartner et al., Nat. Nanotech. 12, 980 (2017).