유재준 교수

Body-centered tetragonal ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ is shown to have its electronic structure and properties dominated by the layered in-plane Cu-3d--O-2p interactions. A strong Fermi surface instability along [110] with \ensuremath{\Vert}q\ensuremath{\Vert}=2${k}_{\mathrm{F}}$ leads, via a soft-phonon mode, to the observed orthorhombic phase and accounts for its semiconducting properties. The addition of divalent metals, i.e., Ba, Sr, suppresses the instability and stabilizes the t

The origin of the electric-field gradients (EFG) at nuclear sites in the high-${\mathit{T}}_{\mathit{c}}$ superconductor ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ is investigated theoretically by means of highly precise local-density full-potential linearized-augmented-plane-wave calculations. In all cases considered (i.e., at Cu, O, Ba, and Y nuclei), the theoretical predictions for the principal axis ${\mathit{V}}_{\mathit{z}\mathit{z}}$ and the anisotropy parameter \ensuremath

With one of the highest intrinsic magnetic moments $(10.6\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{atom})$ among the heavy rare-earth elements, dysprosium exhibits a rich magnetic phase diagram, including several modulated magnetic phases. Aided by the Ruderman-Kittel-Kasuya-Yosida interaction, the magnetic modulations propagate coherently over a long range. Neutron diffraction experiments were performed to determine the microscopic magnetic origin of the field induced phases in

Using elastic neutron scattering on single crystals of ${\text{La}}_{1\ensuremath{-}x}{A}_{x}{\text{CoO}}_{3}$ ($A={\text{Ca}}^{2+}$, ${\text{Sr}}^{2+}$, and ${\text{Ba}}^{2+}$), we found the development of magnetic superstructures below the global magnetic transition to be strongly dependent on the size of the $A$-site dopant, $⟨{r}_{A}⟩$, in an unusual way. Upon reducing the $⟨{r}_{A}⟩$ (i.e., as with Ca doping), only a commensurate ferromagnetic cluster phase is evident. On expanding the $⟨{r

Kagome metal-organic frameworks (MOFs) are considered a new class of materials that can host two-dimensional (2D) magnetism and correlated electron phenomena such as superconductivity and quantum anomalous Hall effect. Despite its potential for spintronics applications and others, the systematic understanding between the electronic structure and magnetic properties of kagome MOFs is still missing. This work determines the crystal structure, magnetic ground states, and anisotropy of a series of t

Pulsed neutron diffraction and inelastic neutron scattering were performed on the orthorhombic perovskite PrCoO${}_{3}$ to investigate possible spin-state transitions arising from Co${}^{3+}$ ions. Although the crystal symmetry is orthorhombic, no evidence for a Jahn-Teller distortion is observed in either the average or local crystal structures, suggesting that the intermediate-spin Co${}^{3+}$ state, if present, does not give rise to a static Jahn-Teller distortion. While previous measurements

We investigate the energetic stability and dissociation dynamics of water adsorption at the LaAlO3 surface of the n-type LaAlO3/SrTiO3 (LAO/STO) interface and its effect on the electronic properties of the interface by carrying out first-principles electronic structure calculations. In an ambient atmosphere at room temperature the configuration of 1 monolayer (ML) of water molecules including 3/4 ML of dissociated water molecules adsorbed at the surface is found to be most stable, whereas the co