• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.88.2-88.2
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• 2000

• Proceedings of the Korean Magnestics Society Conference
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• 1996.05a
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• pp.82-83
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• 1996

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.68.1-68
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• 2000

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.157.2-157
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• 2000

• Journal of the Korean Magnetics Society
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• v.9 no.6
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• pp.278-284
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• 1999

The effect of TiO$_2$addition has been studied on the power loss, density, initial permeability, resistivity, and microstructure of Mn-Zn ferrites. TiO$_2$addition increased the density of sintered body and decreased of the initial permeability. Activation energy for electron hopping as well as electrical resistivity increased with TiO$_2$addition. The toroidal core sintered at 1150 $^{\circ}C$ with 1.5 wt% of TiO$_2$demonstrated the power loss of 83 mW/㎤ at 1 MHz, 25 mT, 8$0^{\circ}C$. However, the same specimen sintered at 120$0^{\circ}C$ lead to the power loss, 1168 mW/㎤ at 1 MHz, 25 mT, 8$0^{\circ}C$ and developed an exaggerated grain growth.

• Journal of electromagnetic engineering and science
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• v.5 no.4
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• pp.161-165
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• 2005

We prepared Mn-Zn ferrite Electromagnetic(EM) wave absorbers. The Mn-Zn ferrite EM wave absorbers were coated with Sr ferrite powders and $Al(OH)_3$ powders. The coated Mn-Zn ferrite EM wave absorbers show improved absorption compared with non-coated Mn-Zn EM wave absorbers.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.68-69
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• 1998

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.1026-1034
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• 1995

It is well known that the addition of CaO-SiO$_2$to Mn-Zn ferrites forms an insulating grain bounary layer with high electrical resistivity. This study investigated the effect of Nb$_2$O$_{5}$ on the electromagnetic properties of high frequency low loss Mn-Zn ferrites. The addition of 300ppm Nb$_2$O$_{5}$ developed an exaggerated grain growth while the addition of CaO-SiO$_2$addition with 200ppm Nb$_2$O$_{5}$ more effectively increased the density than that without Nb$_2$O$_{5}$. The addition of Nb$_2$O$_{5}$ showed the lower power loss below 100 ppm SiO$_2$and the Nb$_2$O$_{5}$-CaO addition lowered the power loss at higher sintering temperature.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.556-560
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• 1991

The behavior of Ni-Zn ferrite/Mn-Zn ferrite composite electromagnetic absorber was investigated. The imaginary part of complex permeability of the composite was higher than that of either ferrite alone at all frequency range (50∼1400MHz) studied. The difference, which was pronounced in low frequency range, was reached the maximum value when the composite consisted of constituent ferrites with equal amount. Since the thickness in inversely proportional to the imaginary part of complex permeability for the ferrite absorber, it was possible to reduce the thickness of electromagnetic absorber by employing a composite of two different ferrites.

• Journal of Magnetics
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• v.21 no.3
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• pp.308-314
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• 2016

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, $Mn_{0.8}Zn_{0.2}Fe_2O_4$ and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The $MnFe_2O_4$ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The $M{\ddot{o}}ssbauer$ spectrum of the $MnFe_2O_4$ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the $M{\ddot{o}}ssbauer$ spectra of the $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, and $Mn_{0.8}Zn_{0.2}Fe_2O_4$ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of the $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explained the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure $MnFe_2O_4$, the saturation magnetizations and coercivities were larger in $Mn_{0.8}Co_{0.2}Fe_2O_4$ and smaller in $Mn_{0.8}Zn_{0.2}Fe_2O_4$, and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.