|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||Apr. 08 (Fri.), 4:00 PM||E6-2. 5st fl. #1501||Dr. Changyoung Kim, SEOUL NATIONAL UNIV.||Spectroscopic studies of iron-based superconductors : what have we learned?|
|251||Sep. 4 (Tue), 02:30 PM||E6-2. 2st fl. #2502||Dr. Changmin Lee, MIT||Ultrafast time- and angle-resolved photoemission spectroscopy (tr-ARPES) with extreme ultraviolet laser pulses|
|250||May. 3 (Fri), 11:00 AM||E6-2. 2st fl. #2502||Prof. Changhee Sohn||Exotic Magnetism|
|249||NOV. 23 (Fri), 03:00 PM||E6-2. 2st fl. #2501||Prof. Sang-Jin Sin||Entanglement string and Spin Liquid with Holographic duality|
|248||JAN. 7 (Mon), 03:00 PM||E6-2. 2st fl. #2501||Dr. Byoung min Kang||Many-Body Invariants for Multipoles in Higher-Order Topological Insulators|
|247||MAR. 26 (TUE), 0300 PM||E6-2. 2st fl. #2501||Prof. Jung Hoon Han||Consideration of thermal Hall effect in frustrated and un-frustrated quantum magnets|
|246||Jun. 18 (MON), 10:00 AM||E6-2. 2nd fl. #2502||Dr. Thibault VOGT||Rydberg electromagnetically induced transparency and microwave-to-optical conversion using Rydberg atoms|
|245||2015/10/16, 4PM||E6-2. 2nd fl. #2501||Prof. Yung-Fu Chen(Solid-state Laser Physics Laboratory,National Central University)||Fluctuations of entropy production in partially masked electric circuits|
|244||2015/09/14, 2PM||E6-2. 2nd fl. #2501||Dr. Hae Ja Lee ( Stanford University, SLAC )||Ultrafast X-ray Studies on Dynamics Matter in Extreme Conditions|
|243||Jan.9 (Wed.), 04:00 PM||E6-2. 2nd fl. #2501||Dr. Heung-Sik Kim||Molecular Mott state in the deficient spinel GaV4S8|
|242||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|
|241||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|
|240||Apr. 01 (Fri.) 2:30 PM||E6-2. 1st fl. #1501||Dr. KICHEON KANG, Chonnam National University||Interference of single charged particles without a loop and dynamic nonlocality|
|239||Apr. 01 (Fri.) 4:15 PM||E6-2. 1st fl. #1501||Dr. JONG SOO LIM, KIAS||Cotunneling drag effect in Coulomb-coupled quantum dots|
|238||Apr. 08 (Fri.), 13:30 PM||E6-2. 1st fl. #1501||Dr. Yunkyu Bang, Chonnam National Univ.||Theoretical Overview of Iron-based superconductors and its future|
|237||Oct. 12 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Daniel Kyungdeock Park||Quantum Advantage in Learning Parity with Noise|
|236||Oct. 12 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. HyungWoo Lee||Direct observation of a two-dimensional hole gas at oxide interfaces|
|235||Apr. 28 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. JeongYoung Park Graduate School of EEWS, KAIST||Hot electron generation at surfaces and its impact to catalysis and renewable energy conversion|
|234||Apr. 12 (Tue.), 4 PM||E6-2. 1st fl. #1323||Dr. Jeehoon Kim, POSTECH||Confinement of Superconducting Vortices in Magnetic Force Microscopy|