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Effect of water intercalation onVOxlayers in dodecylamine-intercalated vanadium oxide nanotubes
Kweon, Hyocheon,Lee, Kyu Won,Lee, Eun Mo,Park, Jitae,Kim, I-M.,Lee, Cheol Eui,Jung, G.,Gedanken, A.,Koltypin, Yu. American Physical Society 2007 Physical review. B, Condensed matter and materials Vol.76 No.4
Coexisting structural phases in a two-dimensional vanadium oxide/surfactant nanostructure
Hyocheon Kweon,이규원,이철의 한국물리학회 2009 Current Applied Physics Vol.9 No.3
A structural study employing X-ray diffraction has been made on a two-dimensional (2D) self-organized compound VOx(C12H28N)y comprising inorganic vanadium oxides and organic dodecylammonium surfactants. Coexisting periodic phases of a 2D centered rectangular structure and a lamellar structure have thus been identified and closely followed as a function of temperature, elucidating the changes in the distinct structures and their interplay in the system.
Structural coherence in dodecylamine-intercalated vanadium oxides
Hyocheon Kweon,Kyu Won Lee,이철의 한국물리학회 2010 Current Applied Physics Vol.10 No.4
Dodecylamine-intercalated vanadium oxides of various structures and vanadium valencies have been synthesized and studied by means of X-ray diffraction, Raman spectroscopy, and X-ray photoemission spectroscopy measurements. The structural coherence, as derived from the Raman spectra, is shown to be dictated by the vanadium valency in the compounds, obtained from the X-ray photoemission spectroscopy measurements. The vanadium valency and structural coherence were also observed to be directly related with the oxygen defect, OH groups and ammonium concentrations, with the hydrogen bonding playing an important role.
Hyocheon Kweon,이규원,이철의,Siegmar Roth 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Room-temperature ferromagnetism, concurrent with antiferromagnetic order, was observed in dodecylamine-intercalated vanadium oxide nanosheets by the magnetization and electron spin resonance measurements. Charge disproportionation arising from charge localization around T_P = 375 K appears to be associated with the ferromagnetic order. The ferromagnetic and the antiferromagnetic spins are found to be exchange-decoupled.
Structure and Magnetism in Dodecylamine-Intercalated Vanadium Oxide Gels
이철의,이규원,Hyocheon Kweon 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
Quasi-two-dimensional dodecylamine-intercalated vanadium-pentoxide gels were studied by using X-ray diffraction and electron spin resonance. Besides giving rise to structural transitions at 230 K and 320 K, the water intercalation is shown to dictate the vanadium valency, as manifested by the temperature-dependent spin susceptibility, which is closely coupled to the interlamellar spacing.
Electron spin resonance of defect-rich vanadium oxide nanotubes
Won Lee, Kyu,Kweon, Hyocheon,Lee, Cheol Eui American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.106 No.4
<P>We have studied defect-rich vanadium oxide nanotubes, with reduced V4+ concentration, by means of x-ray diffraction, infrared spectroscopy, x-ray photoemission spectroscopy, and electron spin resonance (ESR) measurements. In particular, prominent anomalies at 320 and 370 K attributed to structural phase transitions were manifest in the ESR measurements. The ESR spin susceptibility exhibited a singlet-triplet transition of the spin dimers and an antiferromagnetic exchange coupling. In the high-temperature region above 370 K, where the two distinct ESR lines merged, an activation energy of the fast hopping polaron motion, 0.48 eV, was obtained. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3208066]</P>
Electron Spin Resonance of Vanadium-Oxide Nanotubes
이규원,이철의,Eun Mo Lee,Hyocheon Kweon,Jitae Park 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.4
Vanadium-oxide nanotubes, synthesized through hydrothermal treatment of a vanadium oxide- alkylamine composite, were studied by means of electron spin resonance (ESR). The ESR spectra were composed of a broad Lorentzian line superposed by a hyper.ne structure, from which the uniaxial g-tensor and the hyper.ne coupling tensor were obtained both for the nanotube and the composite. The eight-line hyper.ne splitting structure appears to indicate that the 3d electrons of the V4+ nuclei interact with only one vanadium nucleus and, thus, are strongly localized. The hyper.ne splitting in the nanotubes was much greater than it was in the V2O5 single crystal, which is apparently ascribable to the curvature of the vanadium-oxide layers.