2014年8月22日（周五）下午2點，量子物質科學協同創新中心清華分中心seminar：

報告題目： Investigation of Interfacial Magnetic Phenomena by Polarized Neutrons and X-rays 報告人： Yaohua Liu Materials Science Division, Argonne National Laboratory 報告時間： 2014-8-22 14:00 報告地點：清華大學物理系理科樓三樓報告廳摘要： 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 [3] C. Bi, Yaohua Liu et al., Giant non-volatile voltage-control of magnetism with full reversibility (unpublished).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). 個人簡曆：劉耀華博士于2009年在美國約翰霍普金斯大學獲物理學博士學位。之後，他在美國阿貢國家實驗室作博士後，并在 2012年後任助理物理學家。他主要利用極化中子和同步輻射X射線研究磁性薄膜和異質結，緻力于探索界面的新現象和功能，以及尋找實現低能耗的電子器件的途徑。他廣泛使用美國多個中子和同步輻射源，包括NIST Center for Neutron Research (NCNR)，Spallation Neutron Source，Los Alamos Neutron Science Center, Advanced Photon Source 和Advanced Light Source。他曾擔任NCNR 的中子束實驗申請的評委，并是PRL, PRB, APL, JMMM等學術期刊的審稿人，也曾為美國中子會議（2014 ACNS）, 2014 APS March Meeting, 國際磁學會議(2013 MMM) 等擔任分會場主席.