• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.326-329
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• 1996

In order to synthesize Ba-ferrite fine particles by molten salt method and inhibit the abnormal grain growth of sintered specimen, KCI anti NaCl were added to basic composition to 50% by weight, and added 1 male% of $SiO_2$ to control the shape of Ba-ferrite particles. $H_{c}$ and $M_{r}$ were decreased when F $e^{3+}$ was substituted with $Co_{2+}$ and $Ti_{4+}$ from x=0 to x=1.0 in $BaFe_{12-2x}$ $Ti_{x}$ $Co_{x}$ $O_{19}$ , and 1 mole% $SiO_2$ increased the size but shortened c-axis of hexagonal ferrite. Seeds added in Ba-ferrite particle effected inhibition of abnormal grain growth during sintering.ing.g.

• Journal of the Korean Magnetics Society
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• v.8 no.1
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• pp.13-20
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• 1998

The crystallographic and high frequency characteristics of $Fe_{73.9}Cu_{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$ soft magnetic alloys were investigated under the magnetic field annealing. As-cast ribbon with which already imbedded nanocrystalline Fe-Si phase on the surface have a preferred orientation with (400) plane to surface and also with the [011] direction parallel to the ribbon length. The extra nanocrystalline Fe-Si phase appeared throughout at 45$0^{\circ}C$ in samples with or without the longitudinal magnetic field. However the formation of nanocrystalline phase does not appear on the suface layer until 50$0^{\circ}C$ annealing temperature under the transverse field. The cryststallization fraction of annealed samples with longitudinal magnetic field is higher than that of samples without magnetic field. When the transverse magnetic field is applied, the crystallization fraction does not increases but decreases until 50$0^{\circ}C$. However the crystallization of internal regions can be confirmed by X-ray diffraction measurement via tilting the sample. It was found that for all samples, the saturation induction were all same with 1.3 T. The coercive field of as-cast sample was 1.06 A/cm, but in annealed samples it decrease from 0.56 to 0.1 A/cm with increasing annealing temperature from 400 and 55$0^{\circ}C$, respectively. The squareness of annealed samples under transverse magnetic field has a small value than that of both without field and with longitudinal field annealing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.545-550
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• 2000

In order to synthesize Ba-ferrite particles by molten salt method KCl and NaCl were added to basic composition to 50% by weight. X was varied from 0.0 to 1.0 to control the magnetic properties in $BaFe_{12-2x}$/ $Co_{x}$ / $Ti_{x}$ / $O_{19}$ and 1 mol% of $SiO_2$was added to control the aspect ratio of hexagonal platelets. And the effects of reaction temperatures were examined by varying the temperature from 85$0^{\circ}C$ to 120$0^{\circ}C$ with 5$0^{\circ}C$ intervals. Eutectic composition of NaCl and KCl lowered the crystallizing temperature of Ba-ferrite in molten salts than using KCl and NaCl separatly. The morphology of resulting Ba-ferrite particles was clearly hexagonal-shaped plates. $H_{c}$ and $M_{r}$ were decreased when F $e^{3+}$ was substitued with $Co^{2+}$ and $Ti^{4+}$ from x=0 to x=1.0 in $BaFe_{12-2x}$/ $Co_{x}$ / $Ti_{x}$ / $O_{19}$ . Adding 1mol% $SiO_2$in molten salt method increased the size but shortened c-axis of the hexagonal ferrites and this result is an opposite phenomenon compared with the result in solid-statge reaction.n.ion.n.

• Korean Journal of Materials Research
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• v.6 no.1
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• pp.90-98
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• 1996

Mn((Cu0.66AI0.34)1-x(Bi0.3Sb0.7)x) 및 Mn((Fe0.66AI0.34)1-x(Bi0.3Sb0.7)x) 합금계의 상의 변화와 자기적 특성을 조사하였다. Mn((Cu, SI)(Bi, Sb)) 합금계는 Bi상, MnSb상, MnBi상, k-상, Heuser상, Mn2Sb 및 $\beta$-Mn상의 혼합상으로 이루어졌으며 x가 증가함에 따라 Bi상과 Mn2Sb상이 증가하고 K-상, Heusler상 및 $\beta$-Mn상이 줄어들거나 사라졌다. 자기적 성질은 자성을 띄는 MnSb상, MnBi상, Mn2Sb상, k-상 및 Hseusler상과 비자성인 Bi상과 $\beta$-Mn상의 상대적 분율에 의해 결정됨을 알 수 있었고, 150K-200K 부근에서 그 이하로 온도가 감소함에 따라 자화값이 급격히 감소하는 현상이 나타났다. Mn((Fe, AI)(Bi, Sb))합금계는 Bi상, MnSb상, MnBi상, MnBi상,$\beta$-Mn상, k-상 및 Mn2Sb상의 혼합상으로 나타났으며, 자기적 성질은 조사한 전 조성에서 강자성을 띄고 있음을 알 수 있었다.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.454-457
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• 2011

We report the preparation of nanocrystalline cobalt ferrite, $CoFe_2O_4$, particles using recycled $Co_3O_4$ and their surface coating with silica using micro emulsion method. Firstly, the $Co_3O_4$ powders were separated from waste cemented carbide with acid-base chemical treatment. The cobalt ferrite nanoparticles with the size 10 nm are prepared by thermal decomposition method using recycled $Co_3O_4$. $SiO_2$ was coated onto the $CoFe_2O_4$ particles by the micro-emulsion method. The $SiO_2$-coated $CoFe_2O_4$ particles were studied their physical properties and characterized by X-ray diffraction (XRD), high resolution-transmission electron microscopy (TEM) analysis and CIE Lab value.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.377-377
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• 2010

FINEMET type nanocrystalline materials synthesized by controlled crystallization of amorphous ribbons[1] exhibit excellent soft magnetic properties making them attractive for technological applications. Present work reports the electronic structure studies of Co-substituted FINEMET to get information on the effect of successive Co substitution on local environment around Fe and Co atom by using near edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) measurements. NEXAFS spectroscopy and XMCD measurements have been carried out at Fe $L_{3,2}$ and Co $L_{3,2}$-edges to investigate the chemical states and electronic structure of FINEMET [$(Fe_{100-x}Co_x)_{78}Si_9Nb_3Cu_1Ba$](0$L_{3,2}$-edge reveal that Fe is in 2+ state and in tetrahedral symmetry with other elements. The magnetic properties exhibiting soft magnetic behavior[2] are discussed on the basis of the electronic structure studied through XMCD.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.226-230
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• 2003

In this study, we analyzed the volcanic rock and scoria samples taken from special sites of Jeju island in two ways at the room temperature. One is the analysis of the chemical composition using X-ray fluorescence spectrometer, the other is the analysis of minerals in the samples, oxidized iron's genus, valence state and magnetic properties using X-ray diffractometry and Mossbauer spectroscopy. We believe that the volcanic rock and scoria samples are chiefly made of silicate minerals, like SiO$_2$, and they also have olivine, pyroxene, ilmenite, hematite and magnetite. The major Fe fractions of the volcanic rock samples are 2+ charge state and those of the scoria samples are 3+ charge state.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.261-268
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• 1995

In order to investigate the origin of the asymmetric magnetization reversal effect, we studied the variation of magnetic hysteresis loops with the alloy composition in amorphous ferromagnetic alloy ribbons of ${(Fe_{1-x}Co_{x})}_{75}Si_{10}B_{15}$ system annealed at $380^{\circ}C$ for 16 hours in a zero field condition. The asymmetric magnetization reversal effect developed more strongly in amorphous ribbons having two metallic components than in ribbons having a single metallic component. The effect developed more strongly in ribbons showing a smaller value of the saturation mag¬netostriction. The development of the asymmetric magnetization reversal effect was affected by the ratio of two metallic components as well as the magnitude of the saturation magnetostriction.

• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.7-13
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• 2002

The studies of non-figure plain coarse pottery from Jeju island is very important because it can explain the characters of plain coarse potteries of the bronze age and the early iron age. In this study, We analyzed the non-figure plain coarse popery from Jeju island in two ways. One is analysis of the chemical composition using X-ray fluorescence spectrometer and X-ray diffraction, the other is analysts of clay mineral contained iron, oxidized iron's genus, valence state and magnetic properties using Mossbauer spectroscopy. We confidence that non-figure plain coarse pottery is chiefly made of silicate minerals, like SiO$_2$. The content of noncrystalline ferrihydrite is supposed to be below 5-10 wt%, non-figure plain coarse pottery is considered to partly consist of Jeju island clay, which is made of neutral volcanic rock and the valence state of iron is Fe$\^$2+/ and Fe$\^$3+/. We presume the reason that the magnetic hyperfine field is lower than that of pure goethite is the change of crystal structure which transforms the combination states of Fe ions while the clay is being fired.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.5
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• pp.413-417
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• 1998

In this paper, we investigate frequency dependance of inductance of FeCoB amorphous magnetic films. $(Fe_{1-x}Co_x)_{79}Si_2B_{19}$ was used as the basic composition of amorphous magnetic film having near zero magnetostriction. The amorphous magnetic films were fabricated with x=0.94 and x=0.95 by using sputtering method at high frequency. The films were anneald under non-magnetic field and near crystallization temperatures(30min at $280^{\circ}C$, 30min and 1hr at $400^{\circ}C$, respectively). As the results of the experiments with the fabricated films, the lowest coercive force was 0.084[Oe] at 400[W] of the input power and the crystallization temperature was $360^{\circ}C$ . In the case 30min at 40$0^{\circ}C$ the inductance value in the low frequency with x=0.95 was higher by 488% than that with x=0.94. The quality factor Q was below 0.7 for all samples. We obtained the highest quality value at 400[KHz] with 30min at $280^{\circ}C$ and x=0.94. The value was about 0.62. Also, the quality factor value was about 0.35 at 1[MHz] with 30min at $280^{\circ}C$ and x=0.95.