2019年度 提案書 （Web公開用）

作成者： Aleksandr Kurenkov （東北大CSIS/CSRN）

研究プロジェクト名： Correlation between antiferromagnetic and ferromagnetic
domain structure in spin‐orbit torque induced memristive magnetization switching.
概要： We propose to study spin‐orbit torque (SOT) switching in antiferromagnet/ferromagnet (AFM/FM)
heterostructures, which have non‐volatile analogue‐like properties. By means of photoemission electron
microscopy (PEEM) coupled with x‐ray magnetic circular and linear dichroism (XMCD and XMLD) we planto study how FM and AFM domains interact and how this explains the unique switching. First experiments,
performed at the Diamond Light Source synchrotron in collaboration with Prof. Gambardella’s group of
ETH yielded domain patterns in FM [Co/Ni] that have never been observed before (see the Figure). We
plan to actively extend this collaborative work to fully reveal what governs the switching process and how
it can be tuned. For that we plan to image AFM domains simultaneously with FM ones, see switching in
nanosized devices and, in perspective, perform time‐resolved measurements.

コアメンバー： Dr. Aleksandr Kurenkov (CSIS/CSRN, Tohoku University), Prof. Shunsuke Fukami, Prof.
Yoshihiko Horio (RIEC, Tohoku University), Prof. Pietro Gambardella and members of his group (ETHZürich, Switzerland), Dr. Francesco Maccherozzi (Diamond Light Source, United Kingdom)
期待される研究成果： Results of this study will
improve fundamental understanding of exchange
bias and SOT switching. Also, they will show apath for engineering customized AFM/FM
analogue‐like and binary devices for conventionaland neuromorphic applications. The chosen
method of PEEM XMCD/XMLD cannot be replacedwith other techniques such as MOKE or transportmeasurements, which increases the value ofobtained knowledge. Preliminary measurementsof the system forecast fruitful and insightful
experiments since both XMCD and XMLD contrast
have been achieved in our system and domain
structure could be reproducibly altered by SOT.

（図面）

XMCD image of
nonvolatile domain
patterns in [Co/Ni]
ferromagnetic
layer, prepared on
top ofantiferromagnetic
PtMn. This yields
memristive SOT
switching of
AFM/FM.

2018年度 報告書 （Web公開用）

作成者： Aleksandr Kurenkov （東北大CSIS/CSRN）

研究プロジェクト名： Correlation between antiferromagnetic and ferromagnetic
domain structure in spin-orbit torque induced memristive magnetization switching.
概要： We studied spin-orbit torque (SOT) switching in antiferromagnet/ferromagnet (AFM/FM)
heterostructures which showed non-volatile analogue-like properties. By means of photoemission
electron microscopy (PEEM) coupled with x-ray magnetic circular and linear dichroism (XMCD andXMLD) we studied how FM domains behave differently depending on the properties of the local
exchange bias and how AFM domains could be switched in a controllable and reproducible mannerby orthogonally directed trains of current pulses.

研究成果（実施状況）： We measured thespin-orbit torque switching of the Neelvector in antiferromagnetic PtMn (seefigure on the left). We could reproducibly
control the state of the antiferromagnetic
by applying trains of 50 pulses of 50 mA in
the orthogonal directions. Switchingmeasurements coupled with XMCD
allowed to characterize different areas of
the ferromagnetic layer and indirectly
characterize the underlying exchange bias
(analysis currently in progress).

AB

主要発表論文等：[1] G. Krisnhnaswamy, A. Kurenkov et al., to be submitted (July 2019).
[2] S. DuttaGupta, A. Kurenkov et al., to be submitted (June 2019).

C2019年度 報告書 （Web公開用）

作成者： Aleksandr Kurenkov（東北大CSIS）

研究プロジェクト名： Correlation between antiferromagnetic and ferromagnetic
domain structure in spin‐orbit torque induced memristive magnetization switching
概要： Research of the dynamics of spin‐orbit torque‐driven magnetization
switching in antiferromagnet/ferromagnet heterostructures for the purpose of using
this non‐linear dynamics for biologically plausible local computations in artificial
synapses and neurons.
研究成果（実施状況）： It was clarified
that switching dynamics is considerably
influenced by temperature dynamics thatoriginates from Joule heating. It allows
measuring time intervals between pulses
because if a pulse arrives shortly after theprevious one, it receives the residual heatand can produce more switching in thesystem. This time measuring mechanism
allows reproducing operation of abiological synapse (Fig. (a)) and a neuron(Fig. (b)).

主要発表論文等： [1] A. Kurenkov et al., Adv. Mater. 31, 1900636 (2019).