• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1066-1068
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• 1999

Magnetic field is commonly used in low temperature processing plasmas in order to obtain high density. E $\times$ B magnetron or surface multipole configuration were most popular. However, the properties of capacitively coupled rf plasma confined by axially applied static magnetic fields have rarely been studied. In this paper, the effects of magnetic field on the characteristics of 13.56MHz/40KHz argon plasma will be reported. Ion saturation current, electron temperature and plasma potential were measured by Langmuir probe and omissive probe. At low pressure region ($\sim$10mTorr), ion current was increased by a factor of 3 - 4 due to reduction of diffusion loss of charged particles to the wall. It was observed that magnetic field induces large time variation of the plasma potential. The experimental result was compared with particle-in-cell simulation. It was also observed that electron temperature tend to decrease with increasing magnetic induction level for 40KHz discharge.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.155-159
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• 2003

Polycrystalline $Ti_{1-x}Co_xO_2$ thin films on $SiO_2$ (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition. Microstructures and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed $Ti_{1-x}Co_xO_2$ thin films with $x{\leq}0.05$ showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the $Ti_{1-x}Co_xO_2$ (TCO) phases. On the other hand, in case of thin films above x=0.05, Co clusters formed in a homogeneous $Ti_{1-x}Co_xO_2$ Phase, and the overall ferromagnetic (FM) properties depended on both $FM_{TCO}$ and $FM_{Co}$. Co clusters with about 10nm-150nm size decreased the value of Mr (the remanent magnetization) and increased the saturation magnetic field.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.393-398
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• 1996

Soft magnetic properties and microstructural evolution of FeTaNC films were investigated, and compared with FeTaN and FeTaC films. Effects of substrate species (glass vs. $CaTiO_3$) on the magnetic properties were also investigated. Co-addition of N and C significantly enhance the grain refinments and magnetism, compared with N or C addition only. Good soft magnetic characteristics of coercivity of 0.17 Oe, permeability of 4000 (5MHz), and saturation flux density of 17 kG can be obtained in the FeTaNC in the relatively wide process windows. While these values appears to be similar to those of FeTaN on glass substrate, most distinctive difference between FeTaNC and FeTaN(or C) is in the effects of substrate. Whereas FeTaNC films show good magnetic characteristics for both glass and $CaTiO_3$ substrates, FeTaN(or C) films show significant degradation on the $CaTiO_3$ substrate.

• Korean Journal of Materials Research
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• v.29 no.4
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• pp.252-257
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• 2019

Fabrication of soft magnetic composite powders for the $Fe_2O_3-Ca$ system by mechanical alloying(MA) has been investigated at room temperature. It is found that soft magnetic composite powders in which CaO is dispersed in ${\alpha}-Fe$ matrix are obtained by MA of $Fe_2O_3$ with Ca for 5 hours. Changes in magnetization and coercivity also reflect the details of the solidstate reduction process of hematite by pure metal of Ca during MA. The saturation magnetization of MA powders increases with increasing MA time and reaches a maximum value of 65 emu/g after 7 hours of MA. The average grain size of ${\alpha}-Fe$ in MA powders, estimated by diffraction line-width, gradually decreases with increasing MA time and reaches 52 nm after 5 hours of MA. It can also be seen that the coercivity of the 5-hour MA sample is fairly high at 190 Oe, suggesting that the grain refinement of already-produced ${\alpha}-Fe$ tends to clearly occur during MA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.23-26
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• 2003

The flat transformer, typically, has a number of parallel single turn secondary windings. Each secondary winding is coupled to the same primary winding. Therefore, the current in each secondary winding is equal to the ampere-turns in the primary winding, and to each other. These characteristics are particularly advantageous where parallel rectifiers are used. The windings share the current equally, with no need for ballast resistors or other added components. In this study, the ferrite magnetic core samples of Mn-Zn system for the Flat transformer are manufactured and the electrical and magnetic characteristics of its tested. The density of sample FO2-2 sintered at $1350^{\circ}C$ is $4.00kg/m^3$, which shows the good microstructural state. The initial permeability and saturation flux density of FO2 at room temperature is 2700 and 510mT, individually. The power loss of FO2 samples at 250kHz have been ranged $350kW/m^3$ to $80kW/m^3$ with temperature. And the minimum power loss of sample FO2-2 showed at $70^{\circ}C$, which property seems very positive to apply for a flat transformer.

• Journal of Powder Materials
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• v.13 no.4 s.57
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• pp.285-289
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• 2006

Co-Fe-Ni-B-Si-Cr based amorphous strips containing nitrogen were manufactured via melt spinning, and then devitrified by crystallization treatment at the various annealing temperatures of $300^{\circ}C{\sim}540^{\circ}C$ for up to 30 minutes in an inert gas $(N_2)$ atmosphere. The microstructures were examined by using XRD and TEM and the magnetic properties were measured by using VSM and B-H meter. Among the alloys, the amorphous ribbons of $Co_{72.6}Fe_{9.8}Ni_{5.5}B_{2.4}Si_{7.1}Cr_{2.6}$ containing 121 ppm of nitrogen showed relatively high saturation magnetization. The alloy ribbons crystallized at $540^{\circ}C$ showed that the grain size of $Co_{72.6}Fe_{9.8}Ni_{5.5}B_{2.4}Si_{7.1}Cr_{2.6}$ alloy containing 121 ppm of nitrogen was about f nm, which exhibited paramagnetic behavior. The formation of nano-grain structure was attributed to the finely dispersed Fe4N particles and the solid-solutionized nitrogen atoms in the matrix. Accordingly, it can be concluded that the nano-grain structure of 5nm in size could reduce the core loss within the normally applied magnetic field of 300A/m at 10kHz.

• Korean Journal of Materials Research
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• v.28 no.7
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• pp.371-375
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• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.91-97
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• 1999

YIG $(Y_3Fe_5O_{12})$ films with 4~80 ${\mu}{\textrm}{m}$ thickness were epitaxially grown on GGG $(Gd_3Ga_5O_{12})$ substrates by LPE (liquid phase epitaxy) techniques. Using various melts having different chemical composition the growth temperature was varied as a parameter. Growth rate, surface morphology, chemical composition, lattice constant, saturation magnetization, and magnetic resonance of the films were investigated. Lattice mismatch between the substrate and film Δa, saturation magnetization, and magnetic resonance line width ΔH increased, decreased, and increased, respectively, as undercooling temperature ΔT increased. The films grown by using the melt with larger R$_1$and smaller R$_3$had smaller ΔH. The major origin of the increase of ΔH was the increase of Δa. It is considered that the magnetic field in the film became locally inhomogeneous with the increase of Δa due to the increase of inhomogenity in stress distribution to the film depth direction. Therefore, in order to grow YIG films with small microwave loss it is necessary to grow films at small ΔT using the melt with large R$_1$and small R$_3$resulting in a small Δa.

• Journal of Magnetics
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• v.20 no.1
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• pp.26-30
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• 2015

The crystallographic and magnetic properties of gallium-substituted cobalt ferrite ($CoGa_xFe_{2-x}O_4$) were investigated. The new material was synthesized using conventional ceramic methods, with gallium substituted for ferrite in the range of x = 0.0 to 1.0, in steps of 0.2. X-ray diffraction and M$\ddot{o}$ssbauer spectroscopy were used to confirm the presence of crystallized particles in the $CoGa_xFe_{2-x}O_4$ ferrite powders. All of the samples exhibited a single phase with a spinel structure, and the lattice parameters decreased as the gallium content increased. The particle size of the samples also decreased as gallium increased. For $x{\leq}0.4$, the M$\ddot{o}$ssbauer spectra of $CoGa_xFe_{2-x}O_4$ could be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe^{3+}$ with A- and B-sites. However, for $x{\geq}0.6$, the M$\ddot{o}$ssbauer spectra could be fitted with two Zeeman sextets and one doublet. The variation in the M$\ddot{o}$ssbauer parameters and the absorption area ratio indicated a cation distribution of $(Co_{0.2-0.2x}Ga_xFe_{0.8-0.6x})[Co_{0.8+0.2x}Fe_{1.2-0.4x}]O_4$, and the magnetic behavior of the samples suggested that the increase in gallium content led to a decrease in the saturation magnetization and in the coercivity.

• Journal of Magnetics
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• v.17 no.2
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• pp.96-99
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• 2012

The change of saturation magnetization in boronized low carbon microalloyed steels was investigated as a function of boronizing time. Specimens were boronized in an electrical resistance furnace for times ranging from 3 to 9 h at 1123 K. The metallurgical and magnetic properties of the specimens were investigated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). A boride layer with saw-tooth morphology consisting of FeB and $Fe_2B$ was observed on the surface, its thickness ranged from 63 ${\mu}m$ to 140 ${\mu}m$ depending on the boronizing time. XRD confirmed the presence of $Fe_2B$ and FeB on the surface. The saturation magnetization decreased with increasing boronizing time. This decrease was attributed to the increased thickness of the FeB and $Fe_2B$ phases. Cracks were observed at the FeB/$Fe_2B$ interfaces of the samples. The number of interfacial cracks increased with increasing boronizing time.