Proceedings of the Korean Magnestics Society Conference (한국자기학회:학술대회 개요집)
The Korean Magnetics Society (KMS)
- Semi Annual
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- 2233-9485(pISSN)
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- 2233-9574(eISSN)
Domain
- Physics > Particle Physics/Field Theory
2011.06a
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Park, Sung-Kyun;Kim, Ki-Yeon;Kim, Ji-Wan;Choi, Hyeok-Cheol;Teichert, A.;You, Chun-Yeol;Shin, Sung-Cheol;Lee, Jeong-Soo;Fitzsimmons, M.R. 3
Since the first discovery of exchange anisotropy on Co/CoO system[1], there have been numerous studies to explore the physical origin of exchange-biased system[2,3]. In this presentation, we report that how the polarized neutron reflectomery can be applied to study the magnetization reversal behavior of the exchange biased system. As an example, the detailed magnetization reversal mechanism of the exchange-biased Py(30 nm)/FeMn (0, 15, 30 nm)/CoFe(30 nm) trilayers was studied and found that the 15 nm antiferromagnetic FeMn layer mediates the magnetization reversal behaviors of both Py and CoFe layers through interlayer exchange bias coupling. We also update the current activities in polarized neutron reflectometer in HANARO. -
Basically, the lattice mismatch between film and substrate can make those BiFeO3(BFO) films distorted with strain structure. BFO phase can be stabilized on LaAlO3(LAO) represents the example of a multiferroic with giant axial ratio. Its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion and related to the rotation of the oxygen octahedra. In this study, we show that phases with a tetragonal-like epitaxial BFO films can indeed be ferroelectric and also can be stabilized via epitaxial growth onto LAO. Recent reports on epitaxial BFO films show that the crystal structure changes from nearly rhombohedral ("R-like") to nearly tetragonal("T-like") at strains exceeding approximately -4.5%, with the "T-like" structure being characterized by a highly enhanced c/a ratio. While both the "R-like" and the "T-like" phases are monoclinic, our detailed x-ray diffraction results reveal asymmetry change from MA and MC type, respectively. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the "T-like" MC phase is reduced, i.e. the system approaches a true tetragonal symmetry. There are two different M-H loops for
$Bi_{1-x}Ba_xFeO_{3-{\delta}}$ (BBFO) and BFO films on SrTiO3(STO) & LAO substrates. Along with the ferroelectric characterization, these magnetic data indicate that the BFO phase stabilized on LAO represents the first example of a multiferroic with giant axial ratio. However, there is a significant difference between this phase and other predicted ferroelectrics with a giant axial ratio: its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion. Therefore, in going from bulk to highly-strained films, a phase sequence of rhombohedral(R)-to-monoclinic ["R-like" MA-to-monoclinic, "T-like" MC-to-tetragonal (T)] is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e. near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone. Those major results are summarized as follows ; 1) Ba-doping increases the unit cell volume, 2) BBFO on LAO can be fully strained up to x=0.08 as a strain limit (Fig. 1), 3) P(E) & M(H) properties can be tuned by the variation of composition, strain, and film thickness. -
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We studied the effect of Dy content on the magnetic properties of cobalt ferrite single crystal. The
$CoFe_{1.9}Dy_{0.1}O_4$ single crystals were grown by the flux method by using$Na_2B_4O_{7.}10H_2O$ (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction test at room temperature confirmed the spinel cubic symmetry with lattice constant a =$8.42{\AA}$ of the single crystals. The presences of constitute elements (Co, Fe and Dy) was endorsedby EDAX analysis. The saturation magnetization (Ms) of$CoFe_{1.9}Dy_{0.1}O_4$ single crystals was measured and is found to be 72emu/g or equivalently$3.2{\mu}B$ /f.u. at 300 K. The observed Ms and coercivity (Hc) is found to be lower than that of pure$CoFe_2O_4$ . -
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Jung, Hyun-Sung;Lee, Ki-Suk;Jeong, Dae-Eun;Choi, Youn-Seok;Yu, Young-Sang;Han, Dong-Soo;Vogel, Andreas;Bocklage, Lars;Meier, Guido;Im, Mi-Young;Fischer, Peter;Kim, Sang-Koog 24
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Park, Youn-Ho;Jang, Hyun-Cheol;Koo, Hyun-Cheol;Kim, Hyung-Jun;Chang, Joon-Yeon;Choi, Heon-Jin;Han, Suk-Hee;Kim, Hi-Jung 37
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Lee, Tae-Young;Ahn, Chi-Yui;Min, Byoung-Chul;Jeong, Bo-Ram;Jang, Soo-Young;Lim, Sang-Ho;Langer, Jurgen;Ocker, Berthold;Maass, Wolfram;Park, Seung-Young;Jo, Young-Hun;Shin, Kyung-Ho 39
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Lee, Yeon-Sub;Min, Byoung-Chul;Ahn, Chi-Yui;Langer, Jurgen;Ocker, Berthold;Maass, Wolfram;Kim, Young-Keun;Shin, Kyung-Ho 41
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Yu, Young-Sang;Lee, Ki-Suk;Jung, Hyun-Sung;Choi, Youn-Seok;Yoo, Myoung-Woo;Han, Dong-Soo;Im, Mi-Young;Fischer, Peter;Kim, Sang-Koog 45
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Han, Dong-Soo;Lee, Jun-Young;Hermsdoerfer, S.J.;Schultheiss, H.;Leven, B.;Hillebrands, B.;Kim, Sang-Koog 46
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Lee, Ha-Na;Sin, So-Won;Min, Gil-Jun;Park, In-Seong;Kim, Hyeong-Jun;Eom, Jong-Hwa;Kim, Tae-Wan 69
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In this study we tried to measure the effect of magnetic field on the dielectric properties of
$BaTiO_3-MgFe_2O_4$ soft magnetic composite. Composites with different weight percents of ferroelectric and ferromagnetic phases were subjected to magnetic field in the order of 0 to 450 Oe and the variation of the dielectric properties was observed. The Variation of dielectric polarization was discussed in terms of Maxwell-Wagner type polarization in particulate composites. -
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변압기, 전동기 등의 에너지 효율을 향상시키기 위해 400 Hz 이상의 주파수에서 사용하는 자성코어 부품의 수요가 증가함에 따라 Si함량이 높은 연자성 코어에 대한 관심이 증가하고 있으며 냉간압연이 어려운 Fe-6.5wt.%Si의 경제적이고 생산성이 높은 분말 성형공정, 주파수에 따른 철손인자들의 영향 및 미세구조 제어에 대한 연구가 체계적이고 지속적 수행되고 있으며 흥미로운 연구결과가 도출되고 있다.
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The limited understanding of the surface properties of
$Pt_3Ni$ for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) has motivated the study of properties and electronic structures of seven layered$Pt_3Ni$ (001), (110), and (111) surfaces. The first principle method based on density functional theory (DFT) is carried out. It is found that the bulk$Pt_3Ni$ has a ferromagnetic ground state with the ordered fcc type L12 structure, which is in good agreement with other results. Non magnetic Pt has the induced magnetic moment due to the strong hybridization between 3d Ni and 5d Pt. The magnetic moment of Pt and Ni enhanced on the surface of each due to surface effect however the magnetic moment of surface Pt in the Pt-segregated Pt3Ni (111) decreased and the magnetic moment of Ni in Ni rich subsurface increased significantly. The calculated d band centers of Pt explain the possibilities for oxygen absorption and play the important roles in altering the catalytic properties. The spin polarized densities of states are presented in order to understand physical properties of Pt in different surfaces in detail. -
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The fundamental properties of
$Fe_3P$ intermetallic compound was investigated in terms of the FLAPW method within GGA. The FM state of$Fe_3P$ was found to be energetically more stable compared to the NM one. It is consistent with the experiment. In addition, the calculated magnetic moments of Fe atoms were calculated to be 2.367, 1.665, and 2.104${\mu}B$ for FeI, FeII, and FeIII atoms, respectively. -
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Choe, Jong-Gu;Park, Gwang-Jun;Son, Il-Ho;Kim, Geun-Ho;Hwang, Do-Geun;Lee, Jang-Ro;Lee, Sang-Seok 147
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Jeon, Byeong-Seo;Seo, Dong-Seok;Jeon, Hyeon-Jun;Kim, Yong-Chan;NamGung, Jeong;Song, Chang-Bin 166
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NamGung, Seok;Lee, Min-U;Park, Yeong-Deok;Jo, In-Sik;Jang, Tae-Seok;Park, Song-Lee;Lee, Seong-Rae 168
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Son, Il-Ho;Kim, Geun-Ho;Choe, Jong-Gu;Jang, Myeong-Su;Nam, Dong-Hyeon;Hong, Yu-Sik;Lee, U-Beom;Lee, Sang-Seok 180
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Kim, Seong-Hyeon;Lee, Jin-Yong;Jang, Tae-Sun;Hwang, Ji-Hyeon;Lee, Hyeon-Suk;Kim, Seon-Uk;Hwang, Do-Geun 196
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