应6163银河net163am与萃英学院的邀请，中国科学院磁性材料与器件重点实验室，中科院宁波材料技术与工程研究所杨洪新研究员来我院访问并做客6163银河net163am“格致﹒创新”论坛第二十三期，欢迎广大师生届时参加！
题目：First-principles study of Dzyaloshinskii-Moriya Interaction
时间：2018年9月7日（星期五），上午9点
地点：格致楼3016报告厅
摘要：
The Dzyaloshinskii-Moriya Interaction (DMI) between spins induced by spin-orbit coupling (SOC) in magnetic materials lacking inversion symmetry and in particular at the interface between ferromagnetic (FM) and heavy nonmagnetic (NM) metals has become recently a subject of tremendous interest for both fundamental research and applications. This is because the DMI is recognized to play the most prominent role for creating topologically non-trivial textures called magnetic Skyrmion which is very attractive for ultra-dense information storage and spintronic devices. Furthermore, DMI plays an essential role for fast domain wall (DW) dynamics driven by spin-orbit torques. It has been shown that the DW velocity strongly depends on the relative parameters of exchange coupling, magnetic anisotropy and the DMI. Thus, much attention has been paid on searching efficient material combinations giving rise to large DMI values at FM/NM interfaces.
Our recent study of DMI at Co/Pt interfaces [1] has unveiled the main features and microscopic mechanisms of DMI in FM/NM bilayers. We found that the large anticlockwise (ACW) DMI of the Co/Pt bilayers has a predominant contribution from pair couplings between the spins of the interfacial Co layer. This DMI between the interface Co spins is directly related to the change of the SOC energy in the interface Pt atoms, demonstrating the picture of Fert-Levy type interfacial DMI from first-principles.
Based on the understanding of the DMI mechanism at FM/NM interfaces [1], we propose several approaches to control the DMI in ultrathin magnetic films and enhance its amplitude. First, the DMI can be enlarged via multilayer stacking of FM and NM metals possessing the required DMI chiralities in corresponding FM/NM bilayers. Next approach is adding an oxidized capping layer, such as MgO, on top of a Co/Pt bilayer. We show that the DMI in MgO/Co/Pt is much larger, about 1.6 times, compared to that in Co/Pt bilayers for all the Co thicknesses considered. [2]
Moreover, we explore the possibility of electric field control of DMI in Oxide/FM/NM structures. [3]
Finally, I’ll report the Rashba effect induced interfacial Dzyaloshinskii-Moriya Interaction at graphene /FM interfaces , which is beyond Fert-Levy type DMI, opening a route creating Skyrmions without heavy metals[4].
[1] H. X. Yang, et al. Physical Review Letters 115, 267210 (2015).
[2] O. Boulle, H. X. Yang et al. Nature Nanotech. 11, 449-454 (2016)
[3] H Yang, O Boulle, V Cros, A Fert, M Chshiev, arXiv preprint arXiv:1603.01847
[4] H. Yang, G. Chen, A. A.C. Cotta, A. T. N'Diaye, S. A. Nikolaev, E. A. Soares, W. A. A. Macedo, A. K. Schmid, A. Fert, M. Chshiev, Nature Materials 17,604（2018）
个人简介：
杨洪新，中国科学院宁波材料技术与工程研究所研究员，博士生导师，中国科学院磁性材料与器件重点实验室副主任。
本科毕业于吉林大学，硕士在吉林大学和中科院物理所联合培养，2012年于法国格勒诺布尔大学获得博士学位，后陆续在巴黎十一大，澳大利亚联邦科学与工业研究中心（CSIRO），SPINTEC，法国国家科学中心和泰雷兹联合物理实验室，以及日本国立材料研究所（NIMS）从事科学研究工作，2017年5月加入宁波材料所。
研究兴趣主要集中在表面界面自旋电子学的理论计算研究，已在Nature Materials,Nature Nanotech.，Phys. Rev. Lett.，Nano Letters，Advanced Materials等杂志上发表论文40余篇，在铁磁金属与氧化物界面自旋电子学，5d和3d金属界面的自旋轨道电子学，自旋霍尔效应以及石墨烯自旋电子学等领域都有文章入选ESI高引用论文。
