|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|
|70||Dec. 8(Thu) 4p.m.||#1323(E6-2. 1st fl.)||Dr. Jinhyoung Lee, Hanyang University||Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator|
|69||Mar. 16 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. JinHee Kim||산화물 다층박막에서의 다양한 물리현상|
|68||Sep. 27 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Jindong Song||0D/1D/2D/3D III-V materials grown by MBE for Optelectronics|
|67||Apr.19 (Fri.), 11:00 AM||#1323, E6-2||Dr. Ji-Sang Park||First-principles studies of semiconductors for solar cell applications|
|66||2015/12/11, 3:45PM||E6-2, #1323||Dr. Ji Hun Sim (POSTECH)||Dynamical mean field theory studies on heavy fermion system|
|65||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|
|64||Apr. 12 (Tue.), 4 PM||E6-2. 1st fl. #1323||Dr. Jeehoon Kim, POSTECH||Confinement of Superconducting Vortices in Magnetic Force Microscopy|
|63||2015/09/07, 3PM||E6-2. 1st fl. #1318||Dr. Jasbinder Sanghera (U.S. Naval Research Laboratory (NRL))||Advanced Optical Materials and Devices at NRL|
|62||Nov. 24(Thu) 4p.m.||#1323(E6-2. 1st fl.)||Dr. Jai-Min Choi, Chonbuk National Univiersity||Harmonic oscillator physics with single atoms in a state-selective optical potential|
|61||October 16 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Jaewon Song||Emergent black holes and monopoles from quantum fields|
|60||Dec. 9(Fri), 1:30 p.m.||#1323(E6-2. 1st fl.)||Dr. Jae Yoon Cho, POSTECH||Entanglement area law in strongly-correlated systems|
|59||Thursday, July 12, 2018 at 17:00||Room 5318, KAIST Natural Sciences Lecture Hall(E6)||Dr. Jae Hyeok Yoo (University of California, Santa Barbara, Department of Physics)||The MilliQan Experiment: Search for Milli-Charged Particles at the LHC|
|58||July 31(Wed.)/ 16:00||E6-2, #1323||Dr. Ivan Borzenets||Features of ballistic superconducting graphene|
|57||Dec. 26 (Wed.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Isaac H. Kim||Brane-like defect in 3D toric code|
|56||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|
|55||July 27, 2018 at 15:00||Room 5318, KAIST Natural Sciences Lecture Hall(E6).||Dr. Hyejung Kim(Technische University Dresden)||Muon g-2 in the 2HDM and MSSM: comprehensive numerical analysis and absolute maxima|
|54||May 13 (Fri.) 4 PM||E6. #1501(1st fl.)||Dr. Hosub Jin, Dept. of Physics, UNIST||Graphene analogue in (111)- BaBiO3 bilayer heterostructures for topological electronics|
|53||Nov. 16 (Wed), 4p.m.||#1323(E6-2. 1st fl.)||Dr. Heung-Sik Kim , University of Toronto||Realizing Haldane Model in Fe-based Honeycomb Ferromagnetic Insulators|
|52||Jan.9 (Wed.), 04:00 PM||E6-2. 2nd fl. #2501||Dr. Heung-Sik Kim||Molecular Mott state in the deficient spinel GaV4S8|
|51||4pm, Sep. 21 (Wed.||E6-2. #2502(2nd fl.)||Dr. Henrik Johannesson , University of Gothenburg (Sweden) and Beijing Computational Science Research Center (China)||Entanglement probe of two-impurity Kondo physics|