|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
|118||Oct. 15, 4pm||(https://kaist.zoom.us/j/93997220310)||정현석 교수님 (SNU)||Towards resource-efficient and fault-tolerant quantum computation with nonclassical light|
|117||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|
|116||May 21 (Tue.), 4:00 PM||#5318, E6-2||임준원 박사||Classification of flat bands according to the band-crossing singularity of Bloch wave functions|
|115||Dec 27 (Fri), 3:00 PM||#5318, E6-2||Han Gyeol Suh||The superconducting order parameter puzzle of Sr2RuO4|
|114||AUG. 31 (Thu.), 2 PM||#5318(E6-2. 5th fl.)||Prof. Hiroaki Ishizuka (The University of Tokyo)||“Berry phase and nonlinear response: photocurrent in noncentrosymmetric insulators and Weyl semimetals”|
|113||Nov. 18th (Fri) 10:30 a.m.||#5318(5th fl.)||Dr. 최 순 원, Havard University||Non-equilibrium many-body spin dynamics in diamond|
|112||Nov. 8 (Wed.), 1:00 PM||#5318 (E6-2. 5th fl.)||Prof. Y. Matsuda Department of Physics, Kyoto University||“Emergent exotic quasiparticles in quantum spin liquids”|
|111||February 21 (Thu.), 16:00 PM||#5313, E6-2||Prof. Diptimoy Ghosh||B-meson charged current anomalies - Theoretical status|
|110||November 20 (Wed.), 4:00 PM||#5302, E6-2||Dr. Shigeyuki Ishida||Correlation between superconducting transition temperature and critical current density in irradiated iron-based superconductors|
|109||June 27 (Thu), 2:00 PM||#2502, E6-2||Hyun-Yong Lee||Gapless Kitaev Spin Liquid to Loop and String Gases|
|108||Sep10(Tue), 15:00||#2502, E6-2||Jun Ho Son||(2+1) D Duality Web from 3D Euclidean Lattice|
|107||April 6 (Fri.), 10:00 AM||#2502, E6||박채연 박사||Entanglement and thermalization in many-body systems: recent progress|
|106||December 13 (Fri.), 1:00 PM||#2501, E6-2||Dr. Chang-Jong Kang||Computational Material Designs: Current Status and Future Directions|
|105||Apr. 28 (Thu.) 3PM||#2501(E6-2. 2nd fl.)||Dr. Chang Hee Sohn, SEOUL NATIONAL UNIVERSITY||Lattice/Spin/Charge Coupling in 5d Pyrochlore Cd2Os2O7|
|104||2019/09/02 - 12/09||Seminar Room 1501||이호성 박사 (한국표준과학연구원) and etc.||Fall 2019: Physics Colloquium|
|103||Oct. 17th (Mon) 11:00 AM||#1323,(E6-2, 1st fl.)||Nguyen Quang Liem, Institute of Materials Science, VAST, Viettnam||IMS and examples of the studies on optoelectronic materials|
|102||October 18 (Thu.), 16:00 PM||#1323, E6-2||Prof. Jongseok Lee||Applications of nonlinear optics for condensed matter researches|
|101||October 4 (Thu.), 16:00 PM||#1323, E6-2||Prof. Soo Jin Kim||Engineering light absorption in an ultrathin semiconductor metafilm|
|100||October 11 (Thu.), 16:00 PM||#1323, E6-2||Prof. Joung-Real Ahn||Dirac electrons in a graphene quasicrystal|
|99||October 15 (Mon.), 16:00 PM||#1323, E6-2||Dr. Yongjoo Baek||Universal properties of macroscopic current-carrying systems|