|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
|322||Sep. 22 (Fri.), 01:00 PM||E6-2. 1st fl. #1323||Dr. EunSeong Kim / Department of Physics, KAIST||Superconductor-metal-insulator transition in thin Tantalum films|
|321||Sep. 14(Mon) 17:30~||Zoom webinar||Teruo Ono (Kyoto U. Japan)||KAIST Global Forum for Spin and Beyond (Third Forum)|
|320||Sep. 13 (Wed.), 4 PM||#1323 (E6-2. 1st fl.)||Prof. Yi. Zhou (The Zhejiang Univ.)||An Introduction to Quantum Spin Liquids|
|319||Sep. 12 (Tue.), 4 PM||#1323 (E6-2. 1st fl.)||Prof. Yi. Zhou (The Zhejiang Univ.)||Exact Solution for the Interacting Kitaev Chain at Symmetric Point|
|318||Sep. 11(Fri), 14:00~||zoom||이관형교수/SNU, 이상윤교수/GIST||SRC Seminar|
|317||Sep. 10 (Tue.), 03:00 PM||E6-2. 1st fl. #1323||Dr. Mikhail Kiselev||Two-Stage Kondo Effect|
|316||Sep. 02(Fri) 4:00 PM||E6-2(1st fl) #1323||Dr. Yong-Joo Doh, Department of Physics and Photon Science, GIST||Quantum Electrical Transport in Topological Insulator Nanowires|
|315||Sep. 02(Fri) 2:30 PM||E6-2(1st fl.), #1323||Dr. Yong-Hyun Kim,Graduate School of Nanoscience and Technology, KAIST||Nanoscale Thermal Physics: Seebeck Effect and Nanoscale Friction|
|314||October 4 (Thu.), 16:00 PM||#1323, E6-2||Prof. Soo Jin Kim||Engineering light absorption in an ultrathin semiconductor metafilm|
|313||October 31 (Thu.), 10:00am||#1323 (E6-2, 1st fl.)||Dr. Seung-Sup Lee||Kondo meets Hubbard: Impurity physics for correlated lattices|
|312||October 29 (Tue.), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Seung-Joo Lee||Particles and Gravity via String Geometry|
|311||October 29 (Tue.), 14:30 PM||#1323, E6-2||Prof. Jörg Wrachtrup||Quantum sensing|
|310||October 29 (Tue.), 10:00am||#1323 (E6-2, 1st fl.)||Prof. Se Kwon Kim||Unconventional Spin Transport in Quantum Materials|
|309||October 26 (Fri.), 4:00 PM||#1323, E6-2||Dr. Kyusung Hwang||Coexisting triple-point and nodal-line topological magnons and thermal Hall effect in pyrochlore iridates|
|308||October 25 (Thu.), 4:00 PM||#1323, E6-2||Dr. Gang Li||Abelian and non-Abelian dark photons|
|307||October 24 (Wed.), 10:30 AM||E6-1, Lecture Room 1501(1F)||Prof. Kerry J. Vahala||Photonic integration of next-generation clocks and Hertz-absolute-accuarcy optical frequenncy synthesizers|
|306||October 19 (Fri.), 10:00 AM||#1323, E6-2||Dr. Jongsoo Yoo||Energy conversion processes during magnetic reconnection in a laboratory plasma|
|305||October 18 (Thu.), 16:00 PM||#1323, E6-2||Prof. Jongseok Lee||Applications of nonlinear optics for condensed matter researches|
|304||October 18 (Thu.), 10:00 AM||#1323, E6-2||Dr. Duyoung Min||Understanding membrane protein folding using single-molecule force techniques|
|303||October 17 (Thu.), 16:00 PM||#1323, E6-2||Prof. Namkyoo Park||Top down manipulation of Waves : From Metamaterials, Correlated Disorder, Quantum Analogy, to Digital Processing|