|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|
|54||2015/10/23-12/4 10:30 AM||E6, #1501||Prof. YongKeun Park & Prof. Tae-Young Yoon||How to write a good scientific paper[Open lecture series]|
|53||Dec.23(Wed), 10:00~16:00||Online||Prof. YongKeun Park (KAIST) and etc.||Online workshop for Quantitative Phase Imaging|
|52||April 6, 2017 (Thu), 4:00 pm||IBS CAPP seminar room, Creation Hall (3F), KAIST Munji Campus||Prof. Youngjoon Kwon (Yonsei University)||For whom the Belle tolls|
|51||Nov. 1 (Tue.) 2:30 pm||Seminar Room #1323(E6-2)||Prof. Youngjoon Kwon, Yonsei Univ.||Search for dark sector particles in the B-factory experiments|
|50||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|
|49||July 25(Thur.),4:00PM||E6-2, #1323||Prof.Bohm-Jung Yang||Band topology of twisted bilayer graphene|
|48||September 18(Wed.), 16:00PM||#1323, E6-2||Prof.David Schuster||Exploring Synthetic Quantum Matter in Superconducting Circuits|
|47||Apr. 27, 2017 (Thu) 4:00 pm||Seminar Room(#1323, E6-2)||Prof.Donghan Lee (Chungnam National Univ.)||반도체 양자점을 이용한 단광자 광원|
|46||Nov. 28 (Tue.), 4:00 PM||#1323 (E6-2. 1st fl.)||Samindranath Mitra, Editor at Physical Review Letters||Physics after the lab and the desk: Your work in PRL|
|45||2015/07/16-07/17||E6-2, 1501||Sang-Wook Cheong (Rutgers Univ.)||KAIST Physics Distinguished Lecture|
|44||2016/09/29-12/13||E6-2, #1323||Sangyoon Han 외||2016 Fall, Physics Seminar Serises|
|43||February 20 (Thu), 4:00 PM||#1323, E6-2||Seunghyun Khim||Unconventional superconductivity in the locally non-centrosymmetric heavy-fermion CeRh2As2|
|42||July 8(Mon), 14:00||E6, #1322||T. L. M. Guedes (Univ. of Konstanz)||Ultrabroadband squeezed pulses and their relation to relativity|
|41||Sep. 14(Mon) 17:30~||Zoom webinar||Teruo Ono (Kyoto U. Japan)||KAIST Global Forum for Spin and Beyond (Third Forum)|
|40||Jun 8 (Tue), 10:00 AM||Zoom webinar||Toshihiko Baba (Yokohama National University, Japan)||Photonic crystal devices for sensing|
|39||Jun 22(Tue) 17:00||Zoom webinar||Wei Han (Peking University, China)||Spintronics meets Quantum Materials|
|38||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|
|37||Jan.28(Thu), 03:00PM||Zoom||Yaroslav Tserkovnyak (UCLA)||Topological Transport of Deconfined Hedgehogs in Magnets|
|36||2016/09/05-12/12 4PM||Natual Scien Bldg.(E6)m #1501||Yeong Kwan Kim 외||Physics Colloquium : 2016 Fall|
|35||Dec.10(Thu), 01:55 PM||Zoom||Yin Wen (University of Tokyo)||Consistency of Boltzmann equation and light dark matter from inflaton decay|