Efficient manipulation of magnetic domain wall by dual spin-orbit torque in synthetic antiferromagnets

人工反強磁性体における二重スピン軌道トルクによる磁壁の効率的な操作

増田 啓人*; 山根 結太*; 土肥 昂尭*; 山崎 匠*; Modak, R.*; 内田 健一*; 家田 淳一   ; Klui, M.*; 高梨 弘毅; 関 剛斎*

Masuda, Hiroto*; Yamane, Yuta*; Dohi, Takaaki*; Yamazaki, Takumi*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Klui, M.*; Takanashi, Koki; Seki, Takeshi*

Current-induced domain-wall motion (CIDWM) in a synthetic antiferromagnet is a key phenomenon for developing potential high-density-packed magnetic domain-wall memory with fast operation. Here, we report CIDWM in the antiferromagnetically-coupled two Co layers through the Ir interlayer sandwiched by the two Pt layers: Pt/Co/Ir/Co/Pt. The top and bottom Pt layers play a role for generating the spin current coming from the spin Hall effect, which gives rise to the dual spin-orbit torque (SOT) acting on the perpendicular magnetizations of the Co layers. Although a simple argument would predict that SOTs from top and bottom Pt layers cancel each other out, the dual SOT nucleates a reversed magnetic domain and drives the CIDWM effectively at current density of the order of 10 A m. This study also examines the effect of antisymmetric interlayer exchange coupling (AIEC) on CIDWM. We find a positive correlation between the magnitude of AIEC and the domain wall velocity whereas the current density required for nucleating the reversed domain shows a negative correlation with the magnitude of AIEC. These facts suggest that the existence of AIEC improves the performance of CIDWM. Our results provide a new avenue to design SOT domain wall devices based on a synthetic antiferromagnet.