A5100723191- Multiferroics and related materials
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Ferroelectric and Piezoelectric Materials
- Electronic and Structural Properties of Oxides
- Magnetic Properties and Synthesis of Ferrites
- Superconductivity in MgB2 and Alloys
- ZnO doping and properties
- Magnetic properties of thin films
- Magnetic Properties of Alloys
- 2D Materials and Applications
- Topological Materials and Phenomena
- Intellectual Capital and Performance Analysis
- Semiconductor materials and devices
- Advanced Thermoelectric Materials and Devices
- Organic and Molecular Conductors Research
- Semiconductor materials and interfaces
- Magneto-Optical Properties and Applications
- Quantum and electron transport phenomena
- Nuclear materials and radiation effects
- Heusler alloys: electronic and magnetic properties
- High-pressure geophysics and materials
Seoul National University
2016-2025
Soongsil University
2020-2021
Bundang Jesaeng Hospital
2017-2020
Korea Institute of Science and Technology
2011-2017
Chosun University
2017
Pusan National University
2017
University of Seoul
2006-2016
Seoul National University of Science and Technology
2016
Yonsei University
1997-2015
Lawrence Berkeley National Laboratory
2015
Transparent electronic materials are increasingly in demand for a variety of optoelectronic applications, ranging from passive transparent conductive windows to active thin-film transistors. BaSnO${}_{3}$ is semiconducting oxide with large band gap more than 3.1 eV. Recently, we discovered that doped few percent La exhibits an unusually high electrical mobility...
We discovered that La-doped BaSnO3 with the perovskite structure has an unprecedentedly high mobility at room temperature while retaining its optical transparency. In single crystals, reached 320 cm^2(Vs)^-1 a doping level of 8x10^19 cm^-3, constituting highest value among wide-band-gap semiconductors. epitaxial films, maximum was 70 4.4x10^20 cm^-3. also show resistance (Ba,La)SnO3 changes little even after thermal cycle to 530 Deg. C in air, pointing unusual stability oxygen atoms and...
We report the observation of highly anisotropic Dirac fermions in a Bi square net ${\mathrm{SrMnBi}}_{2}$, based on first-principles calculation, angle-resolved photoemission spectroscopy, and quantum oscillations for high-quality single crystals. found that dispersion is generally induced $(\mathrm{SrBi}{)}^{+}$ layer containing double-sized net. In contrast to commonly observed isotropic cone, cone ${\mathrm{SrMnBi}}_{2}$ with large momentum-dependent disparity Fermi velocities...
Infrared reflectivity spectra were measured for a polycrystalline ${\mathrm{La}}_{0.7}$${\mathrm{Ca}}_{0.3}$Mn${\mathrm{O}}_{3}$ sample. The internal phonon modes, i.e., the bending and stretching of Mn${\mathrm{O}}_{6}$ octahedra show significant frequency shifts near Curie temperature ${T}_{C}$. modes found to have linear relationship with excess lattice expansion above ${T}_{C}$, which deviates from prediction Gr\"uneisen law. A strong electron-phonon coupling crossover small large...
We report a significant enhancement of the upper critical field $H_{c2}$ different $MgB_2$ samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals resistivities $\rho$, we show clear trend increase as $\rho$ increases. One particular high resistivity film had zero-temperature $H_{c2}(0)$ well above values competing non-cuprate superconductors such $Nb_3Sn$ Nb-Ti. Our high-field transport measurements give record $H_{c2}^\perp (0) \approx 34T$ $H_{c2}\|(0) 49 T$...
We show that low field magnetoelectric (ME) properties of helimagnets Ba0.5Sr1.5Zn2(Fe1-xAlx)12O22 can be efficiently tailored by Al-substitution level. As x increases, the critical magnetic for switching electric polarization is systematically reduced from ~1 T down to mT, and ME susceptibility greatly enhanced reach a giant value 2.0 10^4 ps/m at an optimum = 0.08. find control nontrivial orbital moment in octahedral Fe sites through crucial fine tuning anisotropy obtaining conspicuously...
We find the realization of large converse magnetoelectric (ME) effects at room temperature in a hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, which rapid change electric polarization low magnetic fields (about 5 mT) is coined to ME susceptibility 3200 ps/m. The modulation magnetization then reaches up 0.62μ(B)/f.u. an field 1.14 MV/m. further that four states induced by different poling exhibit unique, nonvolatile versus curves, can be approximately described effective free energy with...
Transparent conducting oxides (TCOs) and transparent oxide semiconductors (TOSs) have become necessary materials for a variety of applications in the information energy technologies, ranging from electrodes to active electronics components. Perovskite barium stannate (BaSnO 3 ), new TCO or TOS system, is potential platform realizing optoelectronic devices observing novel electronic quantum states due its high electron mobility, excellent thermal stability, transparency, structural...
Transparent oxides are essential building blocks to many technologies, ranging from components in transparent electronics, conductors, absorbers and protection layers photovoltaics photoelectrochemical devices. However, thus far, it has been difficult develop p-type with wide band gap high hole mobility; current state-of-art have mobility the range of < 10 cm$^2$/Vs, much lower than their n-type counterparts. Using high-throughput computational screening guide discovery novel mobility, we...
We report a Fe K$\ensuremath{\beta}$ x-ray emission spectroscopy study of local magnetic moments in various iron-based superconductors their paramagnetic phases. Local are found all samples studied: PrFeAsO, $\mathrm{Ba}{(\mathrm{Fe},\mathrm{Co})}_{2}{\mathrm{As}}_{2}$, LiFeAs, Fe${}_{1+x}$(Te,Se), and ${\mathrm{A}}_{2}{\mathrm{Fe}}_{4}{\mathrm{Se}}_{5}$ (where $\text{A}=\text{K}$, Rb, Cs). The moment size is independent temperature or carrier concentration but varies significantly across...
Magnetoelectric nanocomposites have been a topic of intense research due to their profound potential in the applications electronic devices based on spintronic technology. Nevertheless, spite significant progress made growth high-quality nanocomposite thin films, substrate clamping effect still remains major hurdle realizing ultimate magnetoelectric coupling. To overcome this obstacle, an alternative strategy fabricating self-assembled ferroelectric-ferrimagnetic bulk heterojunction flexible...
<italic>H</italic>-induced stair-like metamagnetic transitions, large magnetocaloric and magnetoelectric effects related to the 4f electrons of rare-earth ions were revealed in chromite crystals.
Realizing a state of matter in two dimensions has repeatedly proven novel route discovering new physical phenomena. Van der Waals (vdW) materials have been at the center these now extensive research activities. They offer natural way producing monolayer simply by mechanical exfoliation. This work demonstrates that possible multiferroic with coexisting antiferromagnetic and ferroelectric orders possibly persists down to bilayer flake NiI$_{2}$. By exploiting optical second-harmonic generation...
We measured thermal conductivity kappa, thermoelectric power S, and electric sigma of La(5/8-x)Pr(x)Ca(3/8)MnO3, showing an intricate interplay between metallic ferromagnetism (FM) charge ordering (CO) instability. The change with temperature (T) x agrees well the effective medium theories for binary metal-insulator mixtures. This agreement clearly demonstrates that variation T as x, relative volumes FM CO phases drastically percolative transition occurs in mixture domains.
Temperature dependent optical conductivity spectra of a ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$ (LCMO) sample were measured. In the metallic regime at very low temperatures, they clearly showed two types absorption features, i.e., sharp Drude peak and broad midinfrared band, which could be explained as coherent incoherent bands large lattice polaron. Electrodynamic analyses suggest that elementary excitation in LCMO should strong coupling have interactions with spin degree freedom.
We present thermodynamic and neutron data on Ni_3V_2O_8, a spin-1 system kagome staircase. The extreme degeneracy of the antiferromagnet is lifted to produce two incommensurate phases at finite T - one amplitude modulated, other helical plus commensurate canted for ->0. H-T phase diagram described by model competing first second neighbor interactions with smaller anisotropic terms. Ni_3V_2O_8 thus provides an elegant example order from sub leading in highly frustrated
We fabricated Pb(Zr0.52Ti0.48)O3-NiFe2O4 composite films consisting of randomly dispersed NiFe2O4 nanoparticles in the Pb(Zr0.52Ti0.48)O3 matrix. The structural analysis revealed that crystal axes are aligned with those ferroelectric has good and magnetic properties. measured transverse longitudinal components magnetoelectric voltage coefficient, which supports postulate effect comes from direct stress coupling between magnetostrictive piezoelectric grains.
Reflectivity spectra of ${\mathrm{CaMnO}}_{3}$ and ${\mathrm{LaMnO}}_{3}$ were measured in a wide photon energy region between 5 meV 30 eV at room temperature. Using the conductivity obtained from Kramers-Kronig analysis, electronic structures manganese oxides investigated. In particular, states near Fermi ${\mathrm{E}}_{\mathrm{F}}$, O 2p Mn 3d (${\mathrm{e}}_{\mathrm{g}}$,${\mathrm{t}}_{2\mathrm{g}}$), studied detail. It was found that band is located closer to ${\mathrm{E}}_{\mathrm{F}}$...
We present powder and single-crystal neutron diffraction bulk measurements of the Kagome-staircase compound Ni3V2O8 (NVO) in fields up to 8.5T applied along c-direction. (The Kagome plane is a-c plane.) This system contains two types Ni ions, which we call "spine" "cross-tie". Our can be described with paramagnetic space group Cmca for T < 15K each observed magnetically ordered phase characterized by appropriate irreducible representation(s). zero-field show that at T_PH=9.1K NVO undergoes a...
We investigate temperature-dependence of the upper critical fields Hc2(T) a superconducting FeTe0.6Se0.4 single crystal by measuring resistivity in static magnetic up to 45 T. The observations strong bending Hc2ab(T) curves and nearly isotropic Hc2ab(0) ~ Hc2c(0) 48 T support presence Pauli paramagnetic effect. show that Werthamer-Helfand-Hohenberg formula considering limiting spin-orbit scattering together can effectively describe both Hc2c(T) curves. enhancement quasi-particle density...
We have investigated the temperature-dependence of upper critical field Hc2(T) in a LiFeAs single crystal by direct measurements resistivity under static magnetic fields up to 36 T. find case H along ab-plane that Hc2ab(0) = 30 T is clearly lower than orbital limiting Hc2orb,ab (0) 39.6 estimated |dHc2ab / dT|Tc, suggesting presence both Pauli- and orbital-limiting effects pair breaking process. The best fit Hc2ab(T) Werthamer-Helfand-Hohenberg formula results Maki parameter {\alpha} 0.9...