김영학 교수

Abstract Magnetic skyrmions are swirling magnetic textures with novel characteristics suitable for future spintronic and topological applications. Recent studies confirmed the room-temperature stabilization of skyrmions in ultrathin ferromagnets. However, such ferromagnetic skyrmions show an undesirable topological effect, the skyrmion Hall effect, which leads to their current-driven motion towards device edges, where skyrmions could easily be annihilated by topographic defects. Recent theoretic

Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical o

We propose a novel origin of magnetic anisotropy to explain the unusual magnetic behaviors of layered ferromagnetic Cr compounds (3d^{3}) wherein the anisotropy field varies from ≲0.01 to ∼3 T on changing the ligand atom in a common hexagonal structure. The effect of the ligand p orbital spin-orbit (LS) coupling on the magnetic anisotropy is explored by using four-site full multiplet cluster model calculations for energies involving the superexchange interaction at different spin axes. Our calcu

Abstract An electride, a generalized form of cavity-trapped interstitial anionic electrons (IAEs) in a positively charged lattice framework, shows exotic properties according to the size and geometry of the cavities. Here, we report that the IAEs in layer structured [Gd 2 C] 2+ ·2e − electride behave as ferromagnetic elements in two-dimensional interlayer space and possess their own magnetic moments of ~0.52 μ B per quasi-atomic IAE, which facilitate the exchange interactions between interlayer

Abstract Lattice distortion, spin interaction, and dimensional crossover in transition metal dichalcogenides (TMDs) have led to intriguing quantum phases such as charge density waves (CDWs) and 2D magnetism. However, the combined effect of many factors in TMDs, such as spin–orbit, electron–phonon, and electron–electron interactions, stabilizes a single quantum phase at a given temperature and pressure, which restricts original device operations with various quantum phases. Here, nontrivial polym

Nanoscale-layered ferromagnets have demonstrated fascinating two-dimensional magnetism down to atomic layers, providing a peculiar playground of spin orders for investigating fundamental physics and spintronic applications. However, the strategy for growing films with designed magnetic properties is not well established yet. Herein, we present a versatile method to control the Curie temperature (TC) and magnetic anisotropy during the growth of ultrathin Cr2Te3 films. We demonstrate an increase o

Abstract Heterogeneous interfaces exhibit the unique phenomena by the redistribution of charged species to equilibrate the chemical potentials. Despite recent studies on the electronic charge accumulation across chemically inert interfaces, the systematic research to investigate massive reconfiguration of charged ions has been limited in heterostructures with chemically reacting interfaces so far. Here, we demonstrate that a chemical potential mismatch controls oxygen ionic transport across TiO

Herein, the size dependent behavior of cobalt ferrite nanoparticles was investigated using synchrotron radiation based techniques.

We investigated the electronic structures of ultrathin SrRuO3 (SRO) films with n = 1, 2, 3, 4, and 8 monolayers (MLs) on SrTiO3 substrates using O K-edge X-ray absorption spectroscopy (XAS). The intensities of the low-energy features reflect the strengths of the Ru 4d-O 2p orbital hybridization. The Ru 4d orbital state evolves with the increasing SRO thickness, exhibiting a crossover at approximately n = 2. For thick SRO films (n ≥ 3), this constitutes a metallic band, while for the 1 or 2 ML fi

Oxygen vacancies and their correlation with the electronic structure are crucial to understanding the functionality of TiO₂ nanocrystals in material design applications. Here, we report spectroscopic investigations of the electronic structure of anatase TiO₂ nanocrystals by employing hard and soft X-ray absorption spectroscopy measurements along with the corresponding model calculations. We show that the oxygen vacancies significantly transform the Ti local symmetry by modu

A new approach to directly organize colloidal particles into patterned arrays using a nanostructured polymer template coated with polyelectrolyte multilayers is introduced. The topological template with both positive and negative charges provides a finely defined chemical nanopattern to guide selective deposition of colloidal particles onto the patterned surface upon Coulombic attraction (see figure).

A novel series of Zn(II) complexes [LnZnCl2] (Ln = LA − LF) based on N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine bidentate ligands, N,N-bis((1H-pyrazol-1-yl)methyl)-3,5-dimethylaniline [LA], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-dimethylaniline [LB], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylaniline [LC], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diisopropylaniline [LD], N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromoaniline [LE] and N,N-bis((1H-pyrazol-1-yl)methyl)benzhydrylamine [LF], has been synthesized a