Computer-Assisted Language Learning for Beginning-Level Nonnative Learners with Special Reference to KLICS: Korean Language in Culture and Society

This is a report on computer-assisted language learning software development project: KLICS, Korean Language in Culture and Society with special focus on its beginning level. It has been built to be used on Apple Macintosh platform in color-capable SuperCard authorware environment. It also can however built to work as a stand-alone software. The article describes three portions of the beginning level software: (1) Hangul: the Korean Alphabet, (2) Pictorial Study and Dialog Practice, and (3) Beginner's Reading

Double-Layer Buffer Template to Grow Commensurate Epitaxial BaBiO3 Thin Films

We propose a BaCeO3/BaZrO3 double-layer buffer template, grown on a SrTiO3 substrate, for epitaxial growth of a target oxide film with large lattice constants of over 4.1 . Lattice mismatch from the substrate was mostly accommodated for by a BaZrO3 arbitrating layer. Having an ideal in-plane lattice structure, BaCeO3 served as the main-buffer to grow the target material. We demonstrated commensurate epitaxy of BaBiO3 (BBO,a = 4.371 ) utilizing the new buffer template. Our results can be applied to heteroepitaxy and strain engineering of novel oxide materials of sizable lattice constants. © Author(s) 20161421sciescopu

Oxygen Partial Pressure during Pulsed Laser Deposition: Deterministic Role on Thermodynamic Stability of Atomic Termination Sequence at SrRuO3/BaTiO3 Interface

With recent trends on miniaturizing oxide-based devices, the need for atomic-scale control of surface/interface structures by pulsed laser deposition (PLD) has increased. In particular, realizing uniform atomic termination at the surface/interface is highly desirable. However, a lack of understanding on the surface formation mechanism in PLD has limited a deliberate control of surface/interface atomic stacking sequences. Here, taking the prototypical SrRuO3/BaTiO3/SrRuO3 (SRO/BTO/SRO) heterostructure as a model system, we investigated the formation of different interfacial termination sequences (BaO-RuO2 or TiO2-SrO) with oxygen partial pressure (PO2) during PLD. We found that a uniform SrO-TiO2 termination sequence at the SRO/BTO interface can be achieved by lowering the PO2 to 5 mTorr, regardless of the total background gas pressure (Ptotal), growth mode, or growth rate. Our results indicate that the thermodynamic stability of the BTO surface at the low-energy kinetics stage of PLD can play an important role in surface/interface termination formation. This work paves the way for realizing termination engineering in functional oxide heterostructures.Comment: 27 pages, 6 figures, Supporting Informatio

Unconventional Anomalous Hall Effect from Antiferromagnetic Domain Walls of Nd\u3csub\u3e2\u3c/sub\u3eIr\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e7\u3c/sub\u3e Thin Films

Ferroic domain walls (DWs) create different symmetries and ordered states compared with those in single-domain bulk materials. In particular, the DWs of an antiferromagnet with noncoplanar spin structure have a distinct symmetry that cannot be realized in those of their ferromagnet counterparts. In this paper, we show that an unconventional anomalous Hall effect (AHE) can arise from the DWs of a noncoplanar antiferromagnet, Nd2Ir2O7. Bulk Nd2Ir2O7 has a cubic symmetry; thus, its Hall signal should be zero without an applied magnetic field. The DWs generated in this material break the twofold rotational symmetry, which allows for finite anomalous Hall conductivity. A strong f−d exchange interaction between the Nd and Ir magnetic moments significantly influences antiferromagnetic (AFM) domain switching. Our epitaxial Nd2Ir2O7 thin film showed a large enhancement of the AHE signal when the AFM domains switched, indicating that the AHE is mainly due to DWs. Our paper highlights the symmetry-broken interface of AFM materials as a means of exploring topological effects and their relevant applications

Unconventional anomalous Hall effect from antiferromagnetic domain walls of N d2 i r2 O7 thin films

Ferroic domain walls (DWs) create different symmetries and ordered states compared with those in single-domain bulk materials. In particular, the DWs of an antiferromagnet with noncoplanar spin structure have a distinct symmetry that cannot be realized in those of their ferromagnet counterparts. In this paper, we show that an unconventional anomalous Hall effect (AHE) can arise from the DWs of a noncoplanar antiferromagnet, Nd2Ir2O7. Bulk Nd2Ir2O7 has a cubic symmetry; thus, its Hall signal should be zero without an applied magnetic field. The DWs generated in this material break the twofold rotational symmetry, which allows for finite anomalous Hall conductivity. A strong f-d exchange interaction between the Nd and Ir magnetic moments significantly influences antiferromagnetic (AFM) domain switching. Our epitaxial Nd2Ir2O7 thin film showed a large enhancement of the AHE signal when the AFM domains switched, indicating that the AHE is mainly due to DWs. Our paper highlights the symmetry-broken interface of AFM materials as a means of exploring topological effects and their relevant applications. © 2018 American Physical Societ

Experimental realization of atomically flat and AlO2-terminated LaAlO3(001) substrate surfaces

Oxide single-crystal substrates with atomically smooth and chemically uniform surfaces are indispensable for constructing sharp epitaxial heterointerfaces and investigating emergent interfacial physical phenomena. Here, we report a simple method to realize atomically flat and AlO2-terminated LaAlO3 (001) [LAO(001)] substrate surfaces. So far, the LAO(001) substrate has been utilized as a structural template for the epitaxial growth of a variety of oxide films. However, well-established methods for achieving atomically flat, singly terminated LAO(001) surfaces have rarely been reported. This is mainly due to the unstable charged surfaces of LaO+ or AlO2-, which hinders simultaneous stabilizations of atomic-scale smoothness and single termination. To overcome this problem, we combined thermal annealing and subsequent deionized water leaching to treat the LAO(001) surface. We used atomic force microscopy to investigate the evolution of the LAO(001) surface during the water leaching and confirmed the atomically flat surface of the 120-min-water-leached sample. We further demonstrated the uniform AlO2 termination of the LAO(001) surface via coaxial impact-collision ion scattering spectroscopy. Using the treated substrates, we are able to grow perovskite oxide films (i.e., SrRuO3) on the LAO(001) substrate with atomically sharp heterointerfaces. Our paper provides an effective means for controlling the surface and interface of transition-metal oxide heterostructures at the atomic scale. © 2019 American Physical Societ

Double-layer buffer template to grow commensurate epitaxial BaBiO3 thin films

We propose a BaCeO3/BaZrO3 double-layer buffer template, grown on a SrTiO3 substrate, for epitaxial growth of a target oxide film with large lattice constants of over 4.1 Å. Lattice mismatch from the substrate was mostly accommodated for by a BaZrO3 arbitrating layer. Having an ideal in-plane lattice structure, BaCeO3 served as the main-buffer to grow the target material. We demonstrated commensurate epitaxy of BaBiO3 (BBO, a = 4.371 Å) utilizing the new buffer template. Our results can be applied to heteroepitaxy and strain engineering of novel oxide materials of sizable lattice constants

Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures

Magnetic skyrmions are topologically protected whirling spin texture. Their nanoscale dimensions, topologically protected stability and solitonic nature, together are promising for future spintronics applications. To translate these compelling features into practical spintronic devices, a key challenge lies in achieving effective control of skyrmion properties, such as size, density and thermodynamic stability. Here, we report the discovery of ferroelectrically tunable skyrmions in ultrathin BaTiO 3 /SrRuO 3 bilayer heterostructures. The ferroelectric proximity effect at the BaTiO 3 /SrRuO 3 heterointerface triggers a sizeable Dzyaloshinskii–Moriya interaction, thus stabilizing robust skyrmions with diameters less than a hundred nanometres. Moreover, by manipulating the ferroelectric polarization of the BaTiO 3 layer, we achieve local, switchable and nonvolatile control of both skyrmion density and thermodynamic stability. This ferroelectrically tunable skyrmion system can simultaneously enhance the integratability and addressability of skyrmion-based functional devices