Yaohua Liu
Materials Science Division, Argonne National Laboratory
时间：8月26日（周二）上午10:30
地点：唐仲英楼A213会议室
Functionalities in complex magnetic heterostructures frequently arise from emergent interfacial phenomena, which require detailed characterization of buried interfaces to reveal the underlying physics. To this respect, interface-sensitive neutron and x-ray techniques are powerful tools to unravel the critical structure-property relationships in magnetic heterostructures. Particularly, x-ray reflectometry (XRR) and polarized neutron reflectometry (PNR) can determine the depth profiles of the chemical structure and the magnetization vector; while X-ray absorption (XAS), X-ray magnetic dichroism (XMD) and linear dichroism (XLD) provide element-specific information on the charge, spin and orbital degrees of freedom. This talk features some of my recent work. (I) Effects of induced magnetization on charge transport at layered oxide interfaces [1,2]. (II) Electric-field control of magnetism in ferromagnetic transition metals [3] and complex oxides [4]. (III) Intrinsic magnetic properties of interfacial phases in exchange-spring magnets [5] and utilization of exchange-spring magnets for investigating ferromagnetism-superconductivity proximity effects [6]. (IV) Interfacial magnetization of highly spin-polarized perovskites and double perovskites [7, 8]. Work at Argonne was supported by the DOE, Office of Science, MSE.
[1] Yaohua Liu et al., Emergent spin filter at a ferromagnetic and insulating layered oxide interface, Phys. Rev. Lett. 111, 247203 (2013). [2] Yaohua Liu et al., Effect of inteface-induced exchange field on cuprate-manganite spin switches, Phys. Rev. Lett. 108, 207205 (2012). [3] C. Bi, Yaohua Liu et al., Giant non-volatile voltage-control of magnetism with full reversibility (unpublished). [4] F.A. Cuellar, Y.H. Liu et al., Reversible electric-field control of magnetization at oxide interfaces, Nat. Commun., 5, 4215 (2014). [5] Yaohua Liu et al., Magnetic structure in Fe/Sm-Co exchange spring bilayers with intermixed interfaces, Phy. Rev. B 83, 174418 (2011). [6] L.Y. Zhu, Yaohua Liu et al., Unanticipated proximity behavior in ferromagnet/superconductor heterostructures with controlled magnetic non-collinearity, Phys. Rev. Lett. 110, 177001 (2013). [7] Yaohua Liu et al., Effects of strain and buffer layer on the interfacial magnetization of Sr2CrReO6 films determined by polarized neutron reflectometry, arXiv:1406.7351. [8] Mark Huijben, Yaohua Liu et al., Enhanced local magnetization by interface engineering in perovskite-type correlated oxide heterostructures (unpublished).
报告人简介:
刘耀华博士于2009年在美国约翰霍普金斯大学获物理学博士学位。 之后，他在美国阿贡国家实验室作博士后， 并在 2012年后任助理物理学家。他主要利用极化中子和同步辐射X射线研究磁性薄膜和异质结，致力于探索界面的新现象和功能，以及寻找实现低能耗的电子器件的途径。 他广泛使用美国多个中子和同步辐射源，包括NIST Center for Neutron Research (NCNR)，Spallation Neutron Source，Los Alamos Neutron Science Center, Advanced Photon Source 和Advanced Light Source。他曾担任NCNR 的中子束实验申请的评委， 并是PRL, PRB, APL, JMMM等学术期刊的审稿人，也曾为美国中子会议（2014 ACNS）, 2014 APS March Meeting, 国际磁学会议(2013 MMM) 等担任分会场主席.