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Jung H. Park Min G. Kim Suk-Jin Ahn Hyun M. Jang 《Journal of magnetism and magnetic materials》2009,321(13):1971-1974
An atomic-scale picture of the strain-mediated magnetoelectric (ME) coupling is delineated by carefully examining the effect of an applied electric field on the extended X-ray absorption fine structure (EXAFS) spectra of a CoFe2O4-dispersed Pb(Zr,Ti)O3 matrix (CFO-PZT) composite. These studies demonstrated a tensile-compressive strain relation between the PZT matrix and the dispersed CFO phase, thereby providing an X-ray spectroscopic evidence of the interfacial strain-mediated ME coupling. Both the dielectric anomaly observed at ∼480 °C and the decrease in the remanent magnetization under an applied electric field support the strain-mediated ME coupling in the CFO-PZT composite. 相似文献
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Young Kyu Jeong Jung-Hoon Lee Suk-Jin Ahn Hyun M. Jang 《Solid State Communications》2012,152(13):1112-1115
We have found that SmFeO3, a family of rare-earth orthoferrites, exhibits temperature-induced magnetization reversal below the critical low-temperature along the a-axis of Pbnm symmetry. First-principles calculations demonstrate that this negative magnetization is mainly attributed to the competition between two magnetocrystalline anisotropy terms in the inequivalent magnetic sites of Sm3+ and Fe3+. Interestingly, the room temperature magnetization-field curve further shows an ultra-fast magnetization switch in the low-magnetic field, suggesting a potential applicability to high-speed magnetic switching devices. 相似文献
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Eun Hye Na Jung-Hoon Lee Suk-Jin Ahn Kun-Pyo Hong Yang Mo Koo Hyun Myung Jang 《Journal of magnetism and magnetic materials》2012
We have studied magnetic structure and properties of Ga-substituted Pb-hexaferrites having the stoichiometry of PbFe12−xGaxO19 with x=6 (i.e., Fe:Ga=1:1). According to the neutron diffraction results, this compound is characterized by a collinear spin structure below its Curie temperature (∼325 K). Analysis of the neutron diffraction patterns further indicates that the magnetic-moment direction of Fe3+ ions located at the octahedral 2a sublattice is downward while that of the unsubstituted PbFe12O19 is upward at room temperature. With decreasing temperature, the Fe3+ magnetic moment at the octahedral 2a sublattice undergoes a reorientation to the upward direction while that of the unsubstituted PbFe12O19 remains upward down to 5 K. This selective local spin reversal at the 2a sublattice of PbFe6Ga6O19 was attributed to the weakening of the superexchange interaction between the octahedral 2a site and the tetrahedral 4fIV site upon the preferential substitution of Ga ions for Fe ions at these two neighboring sites. Comparison of the neutron diffraction results with dc magnetization responses and ac susceptibilities further indicates that the paramagnetic–ferrimagnetic transition at ∼325 K (Tc) is followed by the local spin reversal at lower temperatures. 相似文献
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This study investigates the Mn-Ti-incorporated mesoporous silicate (Mn-Ti-MPS) as a photocatalyst for highly concentrated toluene removal in a plasma-photocatalytic hybrid system. Various Mn-Ti-MPS [Ti/Si molar ratio = 1/4, Mn/Ti molar ratio = 0.01/1 (1 mol%), 0.05/1 (5 mol%) and 0.1/1 (10 mol%)] photocatalysts were successfully synthesized using a common hydrothermal method without causing any structural damage. In the X-ray diffraction (XRD) pattern, the main peaks of the TiO2 anatase structure and MnO did not show. All samples displayed hexagonal specific peaks at 2.5° (d1 0 0 plane), 4.1° (d1 1 0 plane) and 4.7° (d2 0 0 plane). This indicates that the Ti ions and Mn ions were well substituted into the Si ion sites in the framework of MCM-41. Their surface areas decreased compared with that of pure MCM-41, while the hexagonal straight pore size was distributed in a range of 2.5-3.5 nm. In the Mn-Ti-MPS, much more water and toluene molecules were absorbed compared to the Ti-MPS. From the X-ray photoelectron spectroscopy (XPS) result, it was determined that the hydrophilicity of the Mn-Ti-MPS was stronger than that of the Ti-MPS. Photocatalytic decomposition for highly concentrated toluene of 1000 ppm increased in the Mn-Ti-MPS when compared with the Ti-MPS, while toluene decomposition on 5 mol% Mn-Ti-MPS was remarkably enhanced to 80% in the plasma system. The conversion to CO2, however, did not improve in the case of the plasma-only system. Nonetheless, in the plasma-photocatalytic hybrid system, the conversion to CO2 for 5 mol% Mn-Ti-MPS reached 43% (in an 800 ppm toluene conversion). 相似文献
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Park Jae-Bum Kim Jin-Seong Kweon Deok-Ho Kweon Dae-Hyuk Seo Jin-Ho Ha Suk-Jin 《Applied biochemistry and biotechnology》2019,189(2):459-470
Applied Biochemistry and Biotechnology - Xylitol is a valuable substance utilized by food and biochemical industries. NAD(P)H-dependent xylose reductase (XR)—encoded by the yeast KmXYL1... 相似文献
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Sung-Chul Lee Jea-Hun Jang Byung-Yong Lee Jun-Sik Kim Misook Kang Sang-Bong Lee Myung-Jae Choi Suk-Jin Choung 《Journal of molecular catalysis. A, Chemical》2004,210(1-2):131-141
We investigated catalytic behavior of iron in CO2 hydrogenation with and without a ruthenium component. Calcined iron-based catalysts were reduced by H2 and characterized by XRD, BET surface area and CO2, CO and C2H4 temperature-programmed desorption (TPD), and tested for CO2 hydrogenation. When Fe-K/γ-Al2O3 was used as a catalyst, CO2 conversion was 36%, but when Fe-Ru-K/γ-Al2O3 was used, CO2 conversion was 41%. The product selectivities for catalysts with and without the ruthenium component were also compared. Fe-K/γ-Al2O3 exhibited higher methane (16 mol%) and C2–C4 selectivity (39.6 mol%) than Fe-Ru-K/γ-Al2O3. The main products obtained with Fe-Ru-K/γ-Al2O3 were higher hydrocarbons such as C5+ hydrocarbons. For Fe-Ru-K/γ-Al2O3, the product distribution followed the Anderson–Schultz–Flory (ASF) distribution. However, in the case of Fe-Ru-K/γ-Al2O3, the hydrocarbon distribution deviates from the ideal ASF distribution. It is concluded that the readsorption rates of the primary hydrocarbon product increase exponentially with chain length in the ruthenium promoted catalytic system. The behavior of catalysts with and without the ruthenium will be explained by the CO2-, CO- and C2H4– profiles. In this study, it was confirmed that ruthenium component promoted the readsorption ability of -olefin, and then the chain length of hydrocarbon is higher. In addition, the microcrystalline wax produced in CO2 hydrogenation was a high-crystalline and olefin-rich hydrocarbon. 相似文献
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Junseo Choi Ji-Young Ban Suk-Jin Choung Jinsoo Kim Haznan Abimanyu Kye Sang Yoo 《Journal of Sol-Gel Science and Technology》2007,44(1):21-28
Mesoporous TiO2/γ-Al2O3 composite granules were prepared by combining sol–gel/oil-drop method, using various titania solution. The product granules
can be used as a photocatalyst or adsorbent in moving, fluidized bed reactors. The phase composition and pore structure of
the granules can be controlled by calcination temperature and using different titania solution. In the photocatalysis of NH3 decomposition, TiO2/γ-Al2O3 granules using Degussa P25 powder treated thermally at 450 °C showed the highest catalytic ability. However, TiO2/γ-Al2O3 granules using titania made by hydrothermal method had comparable performance in NH3 decomposition. 相似文献
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Jeong YK Lee JH Ahn SJ Song SW Jang HM Choi H Scott JF 《Journal of the American Chemical Society》2012,134(3):1450-1453
Multiferroics have received a great deal of attention because of their fascinating physics of order-parameter cross-couplings and their potential for enabling new device paradigms. Considering the rareness of multiferroic materials, we have been exploring the possibility of artificially imposing ferroelectricity by structurally tailoring antiferromagnets in thin-film forms. YbFeO(3) (YbFO hereafter), a family of centrosymmetric rare-earth orthoferrites, is known to be nonferroelectric (space group Pnma). Here we report that a YbFO thin-film heterostructure fabricated by adopting a hexagonal template surprisingly exhibits nonferroelastic ferroelectricity with the Curie temperature of 470 K. The observed ferroelectricity is further characterized by an extraordinary two-step polarization decay, accompanied by a pronounced magnetocapacitance effect near the lower decay temperature, ~225 K. According to first-principles calculations, the hexagonal P6(3)/mmc-P6(3)mc-P6(3)cm consecutive transitions are primarily responsible for the observed two-step polarization decay, and the ferroelectricity originates from the c-axis-oriented asymmetric Yb 5d(z(2))-O 2p(z) orbital hybridization. Temperature-dependent magnetization curves further reveal an interesting phenomenon of spontaneous magnetization reversal at 83 K, which is attributed to the competition between two distinct magnetocrystalline anisotropy terms, Fe 3d and Yb 4f moments. 相似文献
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