18:15 〜 18:30
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[5p-C18-19] Quantification of Dzyaloshinskii-Moriya interaction from thermally-activated and
flow regime domain wall motion
キーワード：Spin orbit interaction, Magnetization and spin dynamics, Spin current
Spin-orbit torque (SOT) induced domain wall (DW) motion in non-magnet/ferromagnet/oxide systems is a promising concept for three terminal spintronics devices. The asymmetry of stack structure results in an interfacial Dzyaloshinskii-Moriya interaction (DMI) which plays a pivotal role for fast SOT-driven DW motion. Thus, understanding the manifestation of DMI-induced effective field (HDMI) is important. Thermally-activated DW motion under magnetic fields (HZ and HX) is proposed to offer quantitative information about HDMI. However, the role of HDMI from this regime is greatly debated and demands a quantitative comparison of HDMI between dynamically different regime of DW motion, i.e., flow regime. Multilayers utilized in this study are W(5)/CoFeB(1.1)/MgO(2)/Ta(1) (W/CoFeB) and Ta(4)/Pt(3)/Co(0.3)/Ni(0.6)/Co(0.3)/MgO(1.5)/Ru(1) (Pt/[Co/Ni]) (in nm). To evaluate DMI from thermally-activated regime, we investigate HX dependence of bubble expansion under HZ. DW velocity (v) vs HX curve indicates HDMI= 14 ± 5 mT for W/CoFeB, whereas miniscule value (HDMI ≈ 0 ± 10 mT) for Pt/[Co/Ni]. We also investigate HX dependence of current-driven DW motion in flow regime for both the samples. The results shows non-zero DMI for both the structures. Only the result for Pt/[Co/Ni] in thermally-activated regime does not agree with previous study. We find that an accurate determination of DMI strength is possible only when DW motion satisfies a creep scaling law for the thermally-activated regime, whereas the flow-regime experiment is versatile for quantification of DMI.