|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
|299||Feb. 25 - Jun 3||Rm. 1501 (E6)||Spring 2019: Physics Colloquium|
|298||-||RM. 1323, E6-2||Spring 2019: Physics Seminar Serises|
|297||August 27 (Tue.), 4:00PM||Rm. 1323, E6||Hiroshi Eisaki||Critical current properties of Fe-based superconductors|
|296||August. 14th (Wed.), 4:00PM,||Rm. 1323, E6||Prof. Nicolas Treps||Quantum Optics, at the heart of quantum metrology and quantum information|
|295||2019. 7. 16(화)||Rm. 1323 (E6-2)||Prof. Sidney Nagel||2019 Physics Distinguished Lecture|
|294||8/19 (Mon), 10:00~11:30, 8/22 (Thur), 10:00~11:30||Rm. 1322, E6-2||Nicolas Treps||Tutorials on Multimode Quantum Optics in the Continuous Variable Regime|
|293||3 PM, 12 Jun (Wed), 2019||Rm# 1323, E6-2||Dr. Minyoung You||The relation between free and interacting fermionic SPT phases|
|292||Apr. 2 (Fri.), 04:00 PM||Online(Zoom)||Dr. Heejun Yang (KAIST)||Van der Waals heterostructures for orbital gating-based phototransistors and electronic spectroscopy|
|291||Apr. 2 (Fri.), 02:30 PM||Online(Zoom)||Dr. Tae Hyun Kim (SNU)||Quantum computing and entanglement generation using trapped ions and photons|
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|289||Nov 17th 12:00 PM||Online(Zoom)||Prof. Qiang Lin (Univ. of Rochester, USA)||Quantum- & Nano-Photonics" 세미나 시리즈|
|288||Mar25(Thur), 04:00PM||Online Seminar (Zoom)||Prof. Atsushi Tokiyasu (Tohoku Univ.)||Search for dark matter axion with Rydberg atoms|
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|286||Jun. 11 (Fri.), 04:00 PM||Online seminar||Dr. Keun Su Kim(Yonsei University)||Pseudogap in surface-doped black phosphorus|
|285||Jun. 11 (Fri.), 02:30 PM||Online seminar||Dr. Jin Woong Cha(KRISS)||Engineering sound waves and vibrations in multi-mode nanomechanical systems|
|284||May. 14 (Fri.), 04:00 PM||Online seminar||Dr. Je-Hyung Kim(UNIST)||Spatial and temporal separation of environmental dephasing sources from solid-state quantum emitters|
|283||May. 14 (Fri.), 02:30 PM||Online seminar||Dr. Suyong Jung(KRISS)||Electrically tunable spin valve effect in vertical van-der-Waals magnetic tunnel junctions|
|282||Jan.28(Thu), 06:00PM||Online Seminar||Alexandre Zagoskin(Loughborough Univ.)||Quantum metamaterials: concept, theory, prototypes and possible applications|
|281||Mar 2 (Tue.), 16:00||Online||Dr. Dmitry Svintsov||Sensitive terahertz detection with graphene-based transistors|
|280||Feb.17(Wed)~19(Fri), 09:00~11:00AM||Online||Prof. Subir Sachdev (Harvard University)||석학 대중 강연 및 강의 시리즈|