[김대연 학생 / 최석봉 교수] 자구벽 속도의 반대칭 성분 발견 및 원리 규명  
Chirality-induced antisymmetry in magnetic domain wall speed
자구벽 속도는 인가 수평 자기장에 대하여 대칭적으로 변하는 것으로 알려져 왔다. 하지만 최근 자기장에 대한 비대칭적 자구벽 속도 변화가 관측되어, 이에 대한 연구가 활발히 연구되고 있는 상황이다. 본 연구에서는 이러한 비대칭적 변화가 기존의 대칭적인 변화 성분에 추가적인 반대칭 성분으로 이루어져 있음을 실험적으로 규명하였다. 또한, 반대칭 성분이 자구벽의 chirality 로부터 기인한다는 것을 규명하였다.

In chiral magnetic materials, numerous intriguing phenomena such as built-in chiral magnetic domain walls (DWs) and skyrmions are generated by the Dzyaloshinskii–Moriya interaction (DMI). The DMI also results in asymmetric DW speeds under an in-plane magnetic field, which provides a useful scheme to measure the strength of the DMI. However, recent findings of additional asymmetries such as chiral damping have inhibited the unambiguous determination of the DMI strength, and the underlying mechanism of overall asymmetries comes under debate. Here, we experimentally investigate the nature of the additional asymmetry by extracting the DMI-induced symmetric contribution from the DW speed. Our results reveal that the additional asymmetry has a truly antisymmetric nature with the typical behavior governed by the DW chirality. In addition, the antisymmetric contribution alters the DW speed by a factor of 100, dominating the overall variation in DW speed. Thus, experimental inaccuracies can be largely removed by calibration with such antisymmetric contributions, enabling the standard DMI measurement scheme.

이 연구 결과는 NPG (Nature Publishing Group) Asia Materials 에 출판되었다.

Dae-Yun Kim, Min-Ho Park, Yong-Keun Park, Joo-Sung Kim, Yune-Seok Nam, Hyeok-Cheol Choi, Duck-Ho Kim, Soong-Geun Je, Byoung-Chul Min, and Sug-Bong Choe, NPG Asia Mater. 10, e464 (2018)
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