A5084526634- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Multiferroics and related materials
- Topological Materials and Phenomena
- Graphene research and applications
- Organic and Molecular Conductors Research
- Quantum and electron transport phenomena
- Magnetism in coordination complexes
- Solid-state spectroscopy and crystallography
- Advancements in Battery Materials
- Supercapacitor Materials and Fabrication
- Superconducting Materials and Applications
- Magnetic properties of thin films
- Superconductivity in MgB2 and Alloys
- 2D Materials and Applications
- High-pressure geophysics and materials
- Advancements in Semiconductor Devices and Circuit Design
- ZnO doping and properties
- Electronic and Structural Properties of Oxides
- Theoretical and Computational Physics
- Copper-based nanomaterials and applications
- Inorganic Chemistry and Materials
Kyungpook National University
2016-2025
National High Magnetic Field Laboratory
2006-2014
Florida State University
2006-2014
Korea Basic Science Institute
2014
Yonsei University
2014
Ewha Womans University
2002-2010
Ewha Womans University Medical Center
2007
We present detailed measurements of the longitudinal resistivity ${\ensuremath{\rho}}_{xx}(T,H)$ and upper critical field ${H}_{c2}$ ${\text{NdFeAsO}}_{0.7}{\text{F}}_{0.3}$ single crystals in strong dc pulsed magnetic fields up to 45 60 T, respectively. found that scale is comparable ${H}_{c2}\ensuremath{\sim}100\text{ }\text{T}$ high-${T}_{c}$ cuprates. ${H}_{c2}(T)$ parallel $c$ axis exhibits a pronounced upward curvature similar what was extracted from earlier on polycrystalline...
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...
Grain boundaries (GBs) are defects in crystal structures, which general known to be highly active toward various electrocatalytic reactions. Herein, we identify the adverse behaviors of GBs for bimetallic platinum–cobalt (Pt–Co) nanocatalysts oxygen reduction reaction (ORR). As model catalysts, GB-rich Pt–Co nanowires (Pt–Co GB-NWs) and single-crystalline SC-NWs) synthesized. They have very similar diameters, Pt-to-Co ratios, Pt-rich surface except GB populations, can precisely controlled by...
A heterojunction photocathode of CuO and CuBi2O4 grown on an FTO substrate (FTO/CuO/CuBi2O4) was synthesized using hydrothermal method followed by spin coating annealing to overcome the bottlenecks encountered in photoelectrochemical (PEC) water splitting application. The synthesis methods, morphological, structural properties, composition each sample under condition are discussed detail. with 15 layers annealed at 450 °C exhibited best PEC performance. Moreover, its current density reached...
Shubnikov-de Haas oscillations reveal at high fields an abrupt reconstruction of the Fermi surface within hidden-order (HO) phase URu2Si2. Taken together with reported Hall effect results, this implies increase in effective carrier density and suggests that field suppression HO state is ultimately related to destabilizing a gap spectrum itinerant quasiparticles. While hydrostatic pressure favors antiferromagnetism detriment state, it has modest on complex H-T diagram. Instead separation...
Single crystals of the new multiferroic Ba3NbFe3Si2O14 have been synthesized and characterized via X-ray diffraction, magnetic susceptibility, NMR, electric polarization measurements. The underlying topology Fe 3+ spins is composed isolated triangular units stacked in 2D layers along c-direction trigonal lattice. Magnetic susceptibility experiments verify spin state iron moments (S = 5/2), large antiferromagnetic interactions with θ −190 K. A cusp lambda-like feature specific heat indicate a...
We report the valley-selective interlayer conduction of ${\mathrm{SrMnBi}}_{2}$ under in-plane magnetic fields. The $c$-axis resistivity shows clear angular magnetoresistance oscillations indicating coherent conduction. Strong fourfold variation peak in reveals that contribution each Dirac valley is significantly modulated by field orientation. This originates from anisotropic Fermi surfaces with strong disparity momentum-dependent coupling. Furthermore, we found a signature broken symmetry...
We report the electronic and transport properties of triangular antiferromagnet PdCrO(2) at high magnetic fields up to 33 T, using measurements de Haas-van Alphen oscillations Hall resistivity. The below ordering temperature T(N) reveal several two-dimensional Fermi surfaces smaller size than those found in nonmagnetic PdCoO(2), consistent with band structure calculations. This evidences surface reconstruction due 120° helical localized Cr spins, suggesting significant coupling itinerant...
Time reversal symmetry (TRS) breaking often generates exotic quantum phases in condensed matter. In superconductors, TRS by an external magnetic field not only suppresses superconductivity but also leads to a novel state called the gapless superconducting state. Here we show that magneto-terahertz spectroscopy provides us with rare opportunity access and explore of Nb thin films. We present complete functional form order parameter for arbitrary field, which fully self-consistent theory is,...
Finding d-electron heavy fermion (HF) states has been an important topic as the diversity in materials can lead to many exotic Kondo effect-related phenomena or new of matter such correlation-driven topological insulator cooperation between long-range magnetism and lattice behavior. Yet, obtaining direct spectroscopic evidence for a HF system elusive date. Here, we report observation behavior antiferromagnetic metal, FeTe, via angle-resolved photoemission spectroscopy (ARPES) transport...
Ferroelectric Ising chain magnet ${\text{Ca}}_{3}{\text{Co}}_{2\ensuremath{-}x}{\text{Mn}}_{x}{\text{O}}_{6}$ $(x\ensuremath{\simeq}0.96)$ was studied in magnetic fields of up to 33 T. Magnetization and neutron-scattering measurements reveal successive metamagnetic transitions from the zero-field $\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\downarrow}$ spin configuration $\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}$...
By extensive studies of both neutron and synchrotron X-ray diffraction, we discover that the structure deviates from well-known Debye–Gruneissen predictions below T N in multiferroic BiFeO 3 . At same time, it exhibits a magnetoelastic effect ∼0.4%, when undergoes spiral magnetic order with an extremely long incommensurate period 630 Å. We show this additional electric polarization is proportional to intensity Bragg peaks. When subjected high fields, our experiments Monte-Carlo simulation...
${\text{Ba}}_{3}{\text{Mn}}_{2}{\text{O}}_{8}$ is a spin-dimer compound based on pairs of $S=1$, $3{d}^{2}$, ${\text{Mn}}^{5+}$ ions arranged triangular lattice. Antiferromagnetic intradimer exchange leads to singlet ground state in zero field. Here we present the first results thermodynamic measurements for single crystals probing high-field ordered states this material associated with closing spin gap excited triplet states. Specific heat, magnetocaloric effect, and torque magnetometry...
We report a de Haas-van Alphen (dHvA) oscillation study on IrTe2 single crystals showing complex dimer formations. By comparing the angle dependence of dHvA oscillations with band structure calculations, we show distinct Fermi surface reconstruction induced by 1/5-type and 1/8-type dimerizations. This verifies that an intriguing quasi-two-dimensional conducting plane across layers is dimerization in both cases. A phase transition to 1/8 higher density reveals local instabilities associated...
The novel electronic state of the canted antiferromagnetic (AFM) insulator, strontium iridate (Sr2IrO4) has been well described by spin-orbit-entangled isospin Jeff = 1/2, but role in transport phenomena remains poorly understood. In this study, antiferromagnet-based spintronic functionality is demonstrated combining unique characteristics Sr2IrO4. Based on magnetic and measurements, large highly anisotropic magnetoresistance (AMR) obtained manipulating domains. First-principles calculations...
Abstract Several Ising-type magnetic van der Waals (vdW) materials exhibit stable ground states. Despite these clear experimental demonstrations, a complete theoretical and microscopic understanding of their anisotropy is still lacking. In particular, the validity limit identifying one-dimensional Ising nature has remained uninvestigated in quantitative way. Here we performed mapping for prototypical vdW magnet FePS 3 first time. Combining torque magnetometry measurements with magnetostatic...
Abstract The anomalous Hall conductivity (AHC) in magnetic materials, resulting from inverted band topology, has emerged as a key adjustable function spin‐torque devices and advanced sensors. Among systems with near‐half‐metallicity broken time‐reversal symmetry, cobalt disulfide (CoS 2 ) proven to be material capable of significantly enhancing its AHC. In this study, the AHC CoS is empirically assessed by manipulating chemical potential through Fe‐ (hole) Ni‐ (electron) doping. primary...
We present an efficient approach for synthesizing thin graphite-coated SiO2 composites (TGCSCs) supercapacitor applications, by encapsulating particles within multilayered graphene using thermal chemical vapor deposition. The TGCSC maintains the original morphology of particles, with graphite layer exhibiting interlayer distance ∼0.34 nm. Surface analysis revealed formation Si–C and SiO–C bonds, which enhanced conductivity overall performance; in addition, acid treatment improved electrode...
Electrical control of quantum magnetic states is essential in spintronic science. Initial studies on the ferromagnetic state were extended to collinear antiferromagnets and, more recently, noncollinear antiferromagnets. However, electrical mechanisms such exotic remain poorly understood. Here, we report first experimental and theoretical example current helical antiferromagnets, arising from competition between antiferromagnetic exchange interlayer Dzyaloshinskii-Moriya interaction new van...
We have grown single crystals of multiferroic double-perovskite Lu2CoMnO6 and studied the directional dependence their magnetic dielectric properties. The ferromagnetic order emerges below TC ~ 48K along crystallographic c axis. Dielectric anomaly arises b axis at TC, contrary to polycrystalline work suggesting ferroelectricity Through strongly coupled states, highly non-linear variation both constant magnetization was achieved in application fields. This concurrent tunability provides an...
We report the pressure-induced topological quantum phase transition of BiTeI single crystals using Shubnikov-de Haas oscillations bulk Fermi surfaces. The sizes inner and outer FSs Rashba-split bands exhibit opposite pressure dependence up to P = 3.35 GPa, indicating pressure-tunable Rashba effect. Above a critical ~ 2 frequency for surface increases unusually with pressure, shows an abrupt shift. In comparison band structure calculations, we find that these unusual behaviors originate from...