|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|
|135||Feb. 12 (Mon), 3:00pm||#C303, (Creation Hall 3F, KAIST Munji Campus)||Dr. Byeongsu Yang, Kamioka Observatory, Univ. of Tokyo||The recent result of XMASS Experiment|
|134||Feb. 1 (Wed.), 2p.m.||#1323(E6-2. 1st fl.)||Dr. Michihisa Yamamoto, Department of Applied Physics, The University of Tokyo||Quantum electron optics using flying electrons|
|133||December 5 (Thu.), 16:00 PM||#1323, E6-2||Prof. Soon-Hong Kwon||Subwavelenth Photonic Devices: From Single Photon Sources to Solar Cell|
|132||December 3 (Tue.), 4:00 PM||#1323, E6-2||Dr. Jong Mok Ok||Toward Quantum Materials with Correlated Oxides|
|131||December 27(Fri.), 15:00||E6-2,#5318||Han Gyeol Suh||The superconducting order parameter puzzle of Sr2RuO4|
|130||December 18 (Tue.), 4:00 PM||#1323, E6-2||Prof. Shin-ichi Uchida||Road to Higher Tc Superconductivity|
|129||December 13 (Fri.), 1:30-4:30 PM||#1323, E6-2||Biophysics Mini-symposium at KAIST|
|128||December 13 (Fri.), 1:00 PM||#2501, E6-2||Dr. Chang-Jong Kang||Computational Material Designs: Current Status and Future Directions|
|127||Dec. 9(Fri), 4p.m.||#1323(E6-2. 1st fl.||Dr. Kun Woo Kim, KIAS||Shift Charge and Spin Photocurrents in Dirac Surface States of Topological Insulator|
|126||Dec. 9(Fri), 1:30 p.m.||#1323(E6-2. 1st fl.)||Dr. Jae Yoon Cho, POSTECH||Entanglement area law in strongly-correlated systems|
|125||Dec. 8(Thu) 4p.m.||#1323(E6-2. 1st fl.)||Dr. Jinhyoung Lee, Hanyang University||Dynamical Resonance between Two Optical Cavities via Optomechanical Oscillator|
|124||Dec. 7 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Joon Ho Jang||Novel probes of interacting electrons in 2D systems|
|123||Dec. 7 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Gyung Min Choi||Spin generation from heat and light in metals|
|122||DEC. 27 (Thu), 04:00 PM||E6-2. 1st fl. #1323||Prof. Na Young Kim||Quantum Innovation (QuIN) Laboratory|
|121||Dec. 26 (Wed.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Isaac H. Kim||Brane-like defect in 3D toric code|
|120||DEC. 26 (Wed), 04:00 PM||E6-1. 3rd fl. #3434||Y. Kim, A. Go, K. Hwang and E.-G. Moon||Informal Workshop on Topology and Correlation|
|119||DEC. 16~18 (Sun~Tue)||E6-2. 1st fl. #1323||Prof. Keisuke Totsuka||Lectures on 2d Conformal Field Theory|
|118||Dec. 15 (Fri.), 9:20 AM||E6-2, Lecture Room #1323||Prof. Jhinhwan Lee 외 9명||Workshop on Magnetism in Unconventional Superconductors 개최|
|117||Dec. 13-14(Wed.-Thu.) 13:30 PM||자연과학동 대형강의실 (1501호)||장기주 교수 외 9명||KAIST-KIAS Joint Workshop in Theoretical Sciences 개최|
|116||Dec. 12th (Mon)||1:30p.m. #1323(E6-2. 1st fl.)||Dongjoon Song , AIST||“Possible symmetry in the phase diagrams of electron- & hole-doped cuprate high-Tc superconductors”|