|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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|252||2015/11/19, 4PM||E6-2, #1323||Dr. Daesu Lee (University of Wisconsin-Madison)||Emergent Collective Phenomena and Functions at Reduced Dimensions|
|251||2015/11/23, 1:30PM||E6-2, #1323||Dr. Michael Park (Stanford University)||What's Beyond the Standard Model? Lessons from Run I and what might come in Run II|
|250||2015/11/24, 4PM||E6-2, #1323||Dr. Kab-Jin Kim (Institute for Chemical Research, Kyoto University, Japan)||Topology-based understanding of spin dynamics in inhomogeneously magnetized systems|
|249||2015/11/28, 10AM||E6-2, #1323||Dr. Suyong Jung (Korea Research Institute of Standards and Science)||Electron Tunneling Spectroscopy of Single and Bilayer Graphene with Hexagonal Boron Nitride as Tunneling Barrier|
|248||2015/12/01, 4PM||E6-2, #1323||Dr. Yeong Kwan Kim(Lawrence Berkeley National Laboratory, USA)||Introducing extra dimensions to spectroscopic studies of advanced quantum materials|
|247||2015/12/02, 4PM||E6-2, #1323||Dr. Dae-Jeong Kim (Dept. of Physics and Astronomy, University of California, Irvine)||Samarium Hexaboride: Is it a Topological insulator?|
|246||2015/12/03, 4PM||E6-2, #1323||Dr. Sang-Yun Lee (3rd institute of Physics, University of Stuttgart, Germany)||Hybrid solid state spin qubits in wide bandgap semiconductors|
|245||2015/12/09, 11AM||E4(KI Building), Connect room (2nd fl.)||Arjun G. Yodh (University of Pennsylvania)||Functional Imaging & Monitoring of Brain & Breast with Diffuse Light|
|244||2015/12/09, 2PM||E6-2, #1323||Arjun G. Yodh (University of Pennsylvania)||SWELLABLE COLLOIDAL PARTICLES ARE SWELL|
|243||2015/12/11, 1:30PM||E6-2, #1323||Dr. KwangYong Choi (Chung-Ang University)||Quantum spin liquid in the 1/3 depleted triangular lattice Ba3(Ru1-xIrx)Ti2O9|
|242||2015/12/11, 3:45PM||E6-2, #1323||Dr. Ji Hun Sim (POSTECH)||Dynamical mean field theory studies on heavy fermion system|
|241||2015/12/17, 11:00AM||E4(KI Building), Matrix Hall (2nd fl.)||Dr. Jung-Hoon Park (Purdue University)||Wavefront engineering for in-vivo Deep brain imaging|
|240||2016/03/07-06/13||E6, 1501||Prof. David Helfman(KAIST) 외||Physics Colloquium : 2016 Spring|
|239||2016/03/11 1:30 PM||E6-2. 1st fl. #1501||Dr. Kwon Park||Topological phases of matter in nonequilibrium: Topology of the Wannier-Stark ladder|
|238||2016/03/11 4 PM||E6-2. 1st fl. #1501||Dr. Tae-Hwan KIM (POSTECH)||Jan. Switching handedness of of chiral solitons in Z4 topological insulators|
|237||2016/03/11-06/09||E6-2, 1501 외||박권(KAIS) 외||Physics Seminar Serises : 2016 Spring|
|236||2016/09/05-12/12 4PM||Natual Scien Bldg.(E6)m #1501||Yeong Kwan Kim 외||Physics Colloquium : 2016 Fall|
|235||2016/09/29-12/13||E6-2, #1323||Sangyoon Han 외||2016 Fall, Physics Seminar Serises|
|234||2016/1/11, 4PM||E6-2, #1323||Dr. B.J.Kim (Max Planck Institute for Solid State Research)||Mott Physics in the Strong Spin-Orbit Coupling Regime|