|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
|174||Thursday, July 12, 2018 at 17:00||Room 5318, KAIST Natural Sciences Lecture Hall(E6)||Dr. Jae Hyeok Yoo (University of California, Santa Barbara, Department of Physics)||The MilliQan Experiment: Search for Milli-Charged Particles at the LHC|
|173||July 9 (Mon.), 14:00 PM||#1323, E6-2||Prof. Cesar A. Hidalgo, MediaLab, MIT||The principles of collective learning|
|172||June 27 (Wed.), 13:30 PM||#1323, E6-2||Dr. Jung Sik Park||Magnetic reversal of artificial spin ice|
|»||June 22 (Fri.), 04:00 PM||#1323, E6-2||Dr. Daniel Sando||Tuning functional properties of BiFeO3 films using strain and growth chemistry|
|170||July 2. 2018 (Monday) 3:00 PM||Seminar Room (C303), Creation Hall (3F), KAIST Munji Campus||Dr. Peter Winter (Argonne National Laboratory)||High Precision Magnetic Field Measurement for the Muon g-2 Experiment|
|169||2018. 6. 22 10:00am ~ 11:50am||E6-6, Lecture Room 119 (1F)||Prof. Sang Bok Lee, Dept. of Chemistry and Biochemistry, Univ. of Maryland||Success in Research Career|
|168||Jun. 18 (MON), 10:00 AM||E6-2. 2nd fl. #2502||Dr. Thibault VOGT||Rydberg electromagnetically induced transparency and microwave-to-optical conversion using Rydberg atoms|
|167||June 14 (THU), 10:00 AM||E6-2, 2nd fl. #2502||Prof. Kenji Toyoda||Phonons and polariton-like particles in trapped ions for quantum computation and quantum simulation|
|166||Jun. 01 (Fri.), 11:00 AM||E6-2. 1st fl. #1323||Dr. Seung Sae Hong||Topological phases in low-dimensional quantum materials|
|165||May 311 (Thu.), 04:00 PM||#1323, E6-2||Prof. Teun-Teun Kim||Dynamic control of optical properties with gated-graphene metamaterials|
|164||May 29 (Tue.), 04:00 PM||#1323, E6-2||Prof. Jae-Won Jang||Investigation on metal nanostructure/semiconductor junction and its applications|
|163||May. 17 (Thu.), 01:30 PM||E6-2. 1st fl. #1323||Prof. Yong-Baek Kim University of Toronto||Quantum Spin Liquid in Kitaev Materials|
|162||May. 11 (Fri.), 04:00 PM||E6-2. 1st fl. #1323||Dr. Nam Kim||암페어 단위 재정의와 단전자 펌프 소자 개발|
|161||May. 11 (Fri.), 02:30 PM||E6-2. 1st fl. #1323||Dr. Kun Woo Kim||Disordered Floquet topological insulators|
|160||May 9 (Wed.), 04:00 PM||#1323, E6-2||Prof. Jong-Soo Rhyee||Recent advances in thermoelectric bulk composites|
|159||April 11 (Wed), 4:00pm||#1323 (E6-2, 1st fl.)||Dr. Young-Sik Ra||Non-Gaussian states of multimode light generated via hybrid quantum information processing|
|158||April 11 (Wed), 1:30pm||#1323 (E6-2, 1st fl.)||Dr. Yongsoo Yang||Probing 3D Structure and Physical Properties of Materials at the Single-Atom Level|
|157||April 13 (Fri.), 10am||#1323 (E6-2, 1st fl.)||Dr. Sungkun Hong||Quantum meets Mechanics: from Quantum Information to Fundamental Research|
|156||Apr. 09 (Mon.), 11:00 AM||E6-2. 1st fl. #1323||Dr. Seung-Sup B. Lee||Doublon-holon origin of the subpeaks at the Hubbard band edges|
|155||April 6 (Fri.), 10:00 AM||#2502, E6||박채연 박사||Entanglement and thermalization in many-body systems: recent progress|