|일시||June 22 (Fri.), 04:00 PM|
|연사||Dr. Daniel Sando|
Univ. of New South Wales, Sydney
Multiferroics – materials with coexisting ferroic orders such as ferroelectricity and (anti)-ferromagnetism – are presently under intense study by virtue of their promise in next-generation data storage devices. Bismuth ferrite (BiFeO3– BFO) is one of the very few that orders above room temperature. In the bulk, BFO is rhombohedral (R), and in thin films  its properties are sensitive to strain [2,3]. The discovery of the epitaxially-stabilized “super tetragonal phase” of BFO (T-BFO)  incited a flurry of research activity focused on understanding the phase transition and its possible functionalities . T-BFO is also multiferroic, with large ferroelectric polarization and antiferromagnetic order , and the strain relaxation-induced T/R phase mixtures and their exceptional piezoelectric responses  continue to intrigue and motivate researchers. A particularly important characteristic of this phase mixture is the interconversion between the R,T phases with an applied electric field . Since the oxygen configuration of the R and T polymorphs is different , the electronic, magnetic, and optical properties can thus be dynamically modulated. An additional rather crucial (and thus far underexplored) aspect of mixed R/T BFO is the role of chemistryin the formation of the metastable T-phase. Since T-BFO is typically fabricated by pulsed laser deposition, growth parameters can be used as a strong handle to tailor film properties and functionalities.
Here I will describe our work on understanding the influence of strain and growth conditions on the optical, magnetic, and ferroelectric properties of BFO films. I will also show that by precisely controlling fabrication conditions, the formation of the mixed R/T phases in BFO films can be completely suppressed for thicknesses above 70 nm. Such an intriguing result is useful for applications where thicker pure T-BFO films are needed, such as for measuring the expected giant polarization, or for precisely controlling the proportions of the various phases. Finally, through analysis of a large set of epitaxial films, it will be shown that the optical band gap of BFO is rather insensitive to a host of growth and processing parameters . Combined with the numerous other functionalities of this material, one can envisage multifunctional devices, for example, that harvest mechanical and solar energy, or to enhance magnetoelectric coupling at these multiferroic phase boundaries.
 Sando et al., J. Phys: Condens. Matt. 26, 473201 (2014).
 Infante et al., PRL 105, 057601 (2010).
 Sando et al., Nat. Mater. 12, 641 (2013).
 Bea et al., PRL 102, 217603 (2009).
 Sando et al., Appl. Phys. Rev. 3, 011106 (2016).
 Zeches et al., Science 326, 977 (2009).
 Sando et al., Adv. Opt Mater. 6, 1700836 (2018).
Department of Physics, KAIST
|공지||2019/09/18 - 12/5||Seminar Room #1323||Prof. David Schuster and etc.||Fall 2019: Physics Seminar Serises|
|공지||2019/09/02 - 12/09||Seminar Room 1501||이호성 박사 (한국표준과학연구원) and etc.||Fall 2019: Physics Colloquium|
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|248||May 16, 2016 (Mon) 4PM||#1323(E6-2, 1st Fl.)||Dr. Daniel Bowring , Fermi National Accelerator Laboratory||Tuning microwave cavities with biased nonlinear dielectrics for axion searches|
|247||Oct. 12 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Daniel Kyungdeock Park||Quantum Advantage in Learning Parity with Noise|
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|245||September 5 (Wed.), 16:00 PM||#1323, E6-2||Dr. Dirk Wulferding||Shining a light on fractional excitations|
|244||Nov. 04 (Fri), 3:00 PM||E6-2. #1323(1st fl.)||Dr. Dohun Kim, Department of Physics and Astronomy, SNU||Quantum information experiments using few electron spins in semiconductors|
|243||Nov. 9 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Donghun Lee||Quantum sensing and imaging with diamond defect centers for nano-scale spin physics|
|242||#1323(E6-2. 1st fl.)||Jul. 10th (Mon), 4pm||Dr. Duk Young Kim Los Alamos National Laboratory||“Intertwined Orders in a Heavy-fermion metal”|
|241||October 18 (Thu.), 10:00 AM||#1323, E6-2||Dr. Duyoung Min||Understanding membrane protein folding using single-molecule force techniques|
|240||2015/08/04, 11PM||B501, Room Red, KI bldg. 5nd fl.||Dr. Eric Jin Ser Lee(Univ. of Manitoba, Canada)||Propagation of ultrasound through two- and three-dimensional strongly scattering media|
|239||Jul. 07 (Thu.) 2PM||#1323(E6-2. 1st fl.)||Dr. Eun Ah Kim, CORNELL UNIV.||Let there be topological superconductors|
|238||Sep. 22 (Fri.), 01:00 PM||E6-2. 1st fl. #1323||Dr. EunSeong Kim / Department of Physics, KAIST||Superconductor-metal-insulator transition in thin Tantalum films|
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|236||May 24 (Tue) 4 PM||E6-2. #1323(1st fl.)||Dr. Euyheon Hwang, SKKU Advanced Institute of Nanotechnology, Sung Kyung Kwan University||Electronic and magnetic properties of 2D transition-metal thiophosphates and tunability of magnetic order with carrier density|
|235||April 4, 2016 (Mon) - April 8, 2016 (Fri)||KAIST Natural Science Building (E6-2), RM #4314||Dr. Fritz Caspers (CERN)||Radio frequency engineering|
|234||Nov. 1st (Tue), 10:30AM||#1323(E6-2 1st fl.)||Dr. Gadi Eisenstein, Technion||Time scale dependent dynamics in InAs/InP quantum dot gain media|
|233||October 25 (Thu.), 4:00 PM||#1323, E6-2||Dr. Gang Li||Abelian and non-Abelian dark photons|
|232||Sep. 22 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. GilHo Lee / Department of Physics, POSTECH||Quantum Electronic Transport in Graphene Hybrid Nanostructures|
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