Jun-Kyu Kang

Differences in the Electronic Structures of Bulk and Powder FeV 2 O 4 Spinel Oxide Investigated by Using Synchrotron Radiation

The electronic structure of ferrimagnetic spinel oxide of has been investigated by employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). The Fe 2p and V 2p XAS spectra show that the valence states of Fe and V ions are mixed-valent states and states, respectively. In Fe 2p XMCD spectra, finite XMCD signals are observed for divalent states only, but not for states. This finding indicates that the magnetic moments of ions are ordered ferromagnetically but that those of ions are cancelled, implying that ions play an important role in determining magnetic properties of .

Soft X-ray Synchrotron-Radiation Spectroscopy Study of [Co/Pd] Multilayers as a Function of the Pd Sublayer Thickness

We have investigated the electronic structures of intermetallic multilayer (ML) films of [Co(2A)/Pd(xA)] (x: the thickness of the Pd sublayer; x = 1 A, 3 A, 5 A, 7 A, 9 A) by employing soft X-ray absorption spectroscopy (XAS) and soft X-ray magnetic circular dichroism (XMCD). Both Co 2p XAS and XMCD spectra are found to be similar to one another, as well as to those of Co metal, providing evidence for the metallic bonding of Co ions in [Co/Pd] ML films. By analyzing the measured Co 2p XMCD spectra, we have determined the orbital magnetic moments and the spin magnetic moments of Co ions in [Co(2A)/Pd(xA)] ML films. Based on this analysis, we have found that the orbital magnetic moments are enhanced greatly when x increases from 1 A to 3 A, and then do not change much for x ≥ 3 A. This finding suggests that the interface spin-orbit coupling plays an important role in determining the perpendicular magnetic anisotropy in [Co/Pd] ML films.

Soft X-ray Synchrotron-Radiation Spectroscopy Study of Half-metallic Mn3Ga Heusler Alloy

By employing photoemission spectroscopy (PES) and soft X-ray absorption spectroscopy (XAS), the electronic structure of the candidate half-metallic antiferromagnet of Mn3Ga Heusler compound has been investigated. We have studied two ball-milled Mn3Ga powder samples, one after annealing and the other without annealing, respectively. Based on the Mn 2p XAS study, we have found that Mn ions are nearly divalent in Mn3Ga and that the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry are both present in Mn3Ga. We have found relatively good agreement between the measured valence-band PES spectrum of Mn3Ga and the calculated density of states, which is in agreement with the half-metallic electronic structure of Mn3Ga.

Photoelectron Spectroscopy Study of the Semiconductor Electrode Nanomaterials for the Dye Synthesized Solar Cell

The electronic structures of the potential candidate semiconductor nanoparticles for dye-sensitized solar cell (DSSC), such as and , have been investigated by employing X-ray photoemission spectroscopy (XPS). The measured X-ray diffraction patterns show that and samples have the single-phase ilmenite-type structure and the inverse spinel structure, respectively. The measured Zn 2p and Sn 3d core-level XPS spectra reveal that the valence states of Zn and Sn ions are divalent (Zn 2+) and tetravalent (Sn 4+), respectively, in both and . On the other hand, the shallow core-level measurements show that the binding energies of Sn 4d and Zn 3d core levels in are lower than those in . This work provides the information on the valence states of Zn and Sn ions and their chemical bonding in and .

Soft x-ray Synchrotron Radiation Spectroscopy Study of Molecule-based Nano Bioparticles Containing Fe

By employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD), the electronic structures of molecule-based nano bioparticles, such as Helicobacter pylori ferritin (H. pylori ferritin), Heme, -type Prussian Blue (M