• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.403-408
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• 2010

The acoustic properties of anti-inflammatory egonol were investigated by using micro-Brillouin scattering spectroscopy, by use of a 6-pass tandem Fabry-Perot interferometer and an optical microscope specially modified for spectroscopic purposes. The measured Brillouin spectrum was composed of a central peak centered at zero and a Brillouin doublet arising from the longitudinal acoustic waves, i.e. propagating density fluctuations. For the first time, the glass transition of egonol was identified to be about $5^{\circ}C$ at which the Brillouin peak position and the half width showed abrupt changes. The substantial damping of acoustic phonons of egonol near the glass transition temperature indicated that the contribution of internal relaxation processes such as small-amplitude librations of side chains to the damping of acoustic phonons may be substantial depending on the internal structure of molecules.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.279-286
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• 2013

Brillouin spectroscopy has been widely used for the investigation of acoustic properties of condensed matters in the hypersonic region. A high-pressure Brillouin spectrometer was set up by combining a diamond anvil cell and a tandem multi-pass Fabry-Perot interferometer. It was successfully applied to liquid ethanol, and the pressure dependence of the sound velocity, the refractive index and other acoustic properties were derived based on the measurements. The detailed optical setup and experimental procedure are described.

• Journal of the Optical Society of Korea
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• v.2 no.2
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• pp.45-49
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• 1998

We have combined Brillouin scattering experiments and fucdamental optics theory to determine the birefringence of single crystals. Double refraction in anisotropic materials give rise to doublet peaks in Brillouin spectra. With the incident plane orthogonal to the optic axis, the birefrigence of the materials can be determined from one spectrum. We present the Brillouin spectra to confirm this fact for a single crystal $PbMoO_4$.

• Journal of the Optical Society of Korea
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• v.5 no.3
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• pp.67-69
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• 2001

An alternative way to determine the birefringence for uniaxial crystals with Brillouin scattering experiments equipped with a Fabry-Perot interferometer is presented. The value of the minimum cavity spacing of the interferometer to observe the birefringence was found, and it is shown that the experimental error of the birefringence could be reduced by increasing the cavity spacing. For a single crystal of $\alpha$-LiIO$_3$, the birefringence was found to be 0.14814$\pm$0.0007 at 514.5 nm.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.230.2-230.2
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• 2007

• Ceramist
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• v.23 no.1
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• pp.101-109
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• 2020

In this study, the phase transition behaviors of lead-free (Na_1/2Bi_1/2TiO₃)_(1-x)-(BaTiO₃)_x (NBT-BT) are investigated by using Brillouin spectroscopy. The elastic properties, sound velocity and absorption coefficient of NBT-BT are characterized as a function of temperature along different crystallographic axes. The temperature dependences of the elastic constants of NBT-BT near the morphotropic phase boundary are determined for the first time. The unpoled NBT-BT single crystals exhibits the typical relaxor behaviors, presenting broad acoustic and dielectric anomalies. The application of electric field induced discontinuous changes in the elastic properties at ~110℃, which indicates field-induced phase transition occurred. The electric field also changes the dielectric constant from more relaxor-like to ferroelectric-like dielectric behavior.

• Nuclear Engineering and Technology
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• v.38 no.5
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• pp.433-436
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• 2006

The implementation of multiplexing techniques combined with advances in neutron optics make the neutron three-axis spectrometers (TAS) an efficient tool to map inelastic response from single crystals over momentum transfer ranges comparable to the size of a single Brillouin zone. Thanks to recent progress in polarization techniques such experiments can be combined relatively easily with neutron polarization analysis, which does not only provide unambiguous separation of response corresponding to structural and magnetic degrees of freedom, but permits a quantitative analysis of the magnetic response anisotropy, often of crucial importance to test theoretical predictions. In the forthcoming decade we therefore expect a further development of the complementary use, rather than competition, of the reactor-based TAS's with time-of-flight (TOF) instruments for single crystal spectroscopy at the existing (ISIS) as well as at the newly built (SNS, J-PARK) pulsed sources.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.14-24
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• 1996

We have investigated atomic and electronic structures of a clean Pd(111) surface using low energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). A typical clean LEED pattern with a 3-fold symmetry has been observed, corresponding to that for an fcc (111) surface. ARPES measurements have been performed along the $\Gamma-M,\Gamma-K,\Gamma-M$TEX> symmetry lines, from which the experimental band structure of Pd(111) has been determined. The experimental band structure and work function of Pd(111) surface are found to agree well with the calculated band structure of bulk Pd and the calculated work function of Pd(111), respectively. However, the peak positions in the experimental band structure are located closer to the Fermi level than in the theoretical band structure by 0.1~0.8 eV, depending on the $\kappa$-points in the Brillouin zone. In additin, the experimental band widths are narrower than the theoretical band widths by about 0.5eV. The effects of the localized surface Pd 4d states and the Coulomb interaction between Pd 4d bulk electrons have been discussed as possible origins of such discrepancies between experiment and theory.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.350-350
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• 2011

The spin structure of Fe over layers on Cu (001), especially in region II is one of the unsolved problem for many years. We study the out - of - plane (OP) Fermi surfaces (FSs) of 7 monolayer Fe/Cu (001) films using angle resolved photo emission spectroscopy (ARPES). Ultrathin Fe was grown on Cu (001) substrate at room temperature and the experimental measurements were carried out at room temperature and low temperature. Fermi surfaces measured about $\frac{1}{4}$ of the Brillouin Zone (BZ) using photon energies ranging from 170 eV to 280 eV. Our results confirmed that ferromagnetic signal at 7 ML Fe on Cu (001) is nearly zero. These results are consistent with our recent x-ray magnetic circular dichroism (XMCD) and surface magneto - optic Kerr effect (SMOKE) experiments. Based on our observations we have made a simple model of this system, which explains all the experimental results.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.67-73
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• 1998

Crystallographic and magnetic properties of perovskite $Gd_{1-x}Sr_xFeO_{3-y}$ (x=0.0, 0.5) substituted $Sr^{2+}$ having larger inoic radius than $Gd^{3+}$ at GdFeO$_3$have been studied by x-ary diffraction, M$\ "{o}$ssbauer spectroscopy, and VSM. The cystal structures are found to be orthorhombic with the lattice parameters : $a_o=5.53\;{\AA},\;b_o=5.608\;{AA},\;C_o=7.724\;{\AA}$ for $Gd_{0.5}Sr_{0.5}FeO_{3-y}$ (x=0.0, 0.5) have been investigated over temperature range from 4.2 to 690 K using the M$\ "{o}$ssbauer technique. The Neel temperatuer of $Gd_{1-x}Sr_xFeO_{3-y}$ system is 690 K with x value of 0.0 and 515 K with x value of 0.5. Analysis of M$\ "{o}$ssbauer spectra Mohr's salt analysis for $Gd_{1-x}Sr_xFeO_{3-y}$ demonstrated the existence of the mixed valence states of iron and the coordination state of $Fe^{3+}$ and $Fe^{4+}$ ions. The Corresponding hyperfine parameters for GdFeO$_3$ are compatible with S=5/2 $Fe^{3+}$ in octahedral cooedination.l cooedination.