• Journal of the Korean Magnetics Society
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• v.13 no.1
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• pp.15-20
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• 2003

Diffusion speed of Cu metal fine particle is fast better than CuO, so it will promote grain growth in sintering. In this paper, the influence on substituting Cu fine particle for CuO of NiCuZn ferrite with basic composition (N $i_{0.204}$C $u_{0.204}$Z $n_{0.612}$ $O_{1.02}$)F $e_{1.98}$ $O_{2.98}$ has been investigated with varying Cu/CuO ratio. The perfect spinel structure of sintered specimen at 90$0^{\circ}C$ was confirmed by the analysis of XRD patterns. The best condition was obtained when the ratio of Cu/CuO was 60%, and the permeability was 1100 and Ms was 87 emu/g in this condition. Cu has influenced on grain growth in sintering, substituting Cu fine particle for CuO could lower sintering temperature over the 3$0^{\circ}C$. After sintering, substituting Cu performed as good as CuO.s CuO.s CuO.

• Journal of Magnetics
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• v.18 no.1
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• pp.21-25
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• 2013

Nickel substituted manganese ferrites, $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$), were fabricated by sol-gel method. The effects of sintering and substitution on their crystallographic and magnetic properties were studied. X-ray diffractometry of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered above 523 K indicated a spinel structure; particles increased in size with hotter sintering. The M$\ddot{o}$ssbauer spectrum of this ferrite sintered at 523 K could be fitted as a single quadrupole doublet, indicative of a superparamagnetic phase. Sintering at 573 K led to spectrum fitted as the superposition of two Zeeman sextets and a single quadrupole doublet, indicating both ferrimagnetic and paramagnetic phase. Sintering at 673 K and at 773 K led to spectra fitted as two Zeeman sextets due to a ferrimagnetic phase. The saturation magnetization and the coercivity of $Mn_{0.6}Ni_{0.4}Fe_2O_4$ ferrite sintered at 773 K were 53.05 emu/g and 142.08 Oe. In $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.6$) ferrites, sintering of any composition at 773 K led to a single spinel structure. Increased Ni substitution decreased the ferrites' lattice constants and increased their particle sizes. The M$\ddot{o}$ssbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and the octahedral sites of the $Fe^{3+}$ ions. The variations of saturation magnetization and coercivity with changing Ni content could be explained using the changes of particle size.

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.146-152
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• 2003

The waste ferrites from magnetic core manufacturing process were used to $CO_2$gas decomposition to avoid the greenhouse effects. The waste ferrites are the mixed powder of Ni-Zn and Mn-Zn ferrites core. In the reduction of ferrites by 5% $H_2/Ar$ mixed gas, the weight loss of ferrites was about 14~16wt%. After the$CO_2$gas decomposition reaction, the weight of the reduced ferrites was increased up to 11wt%.$CO_2$gas was decomposed by oxidation of Fe and FeO in reduced compound and the phase of the waste ferrite was changed to spinel structure. A new technique capable of$CO_2$decomposition as low cost process through utilizing waste ferrite was development.

• Journal of Magnetics
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• v.15 no.4
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• pp.159-164
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• 2010

The Zn, Co and Ni substituted manganese ferrite powders, $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$, were fabricated by the solgel method, and their crystallographic and magnetic properties were studied. The Zn substituted manganese ferrite, $Zn_{0.2}Mn_{0.8}Fe_2O_4$, had a single spinel structure above $400^{\circ}C$, and the size of the particles of the ferrite powder increased when the annealing temperature was increased. Above $500^{\circ}C$, all the $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$ ferrite had a single spinel structure and the lattice constants decreased with an increasing substitution of Zn, Co, and Ni in $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$. The Mossbauer spectra of $Mn_{1-x}Zn_xFe_2O_4$ (0.0$\leq$x$\leq$0.4) could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. For x = 0.6 and 0.8 they showed two Zeeman sextets and a single quadrupole doublet, which indicated they were ferrimagnetic and paramagnetic. And for x = 1.0 spectrum showed a doublet due to a paramagnetic phase. For the Co and Ni substituted manganese ferrite powders, all the Mossbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The variation of the Mossbauer parameters are also discussed with substituted Zn, Co and Ni ions. The increment of the saturation magnetization up to x = 0.6 in $Mn_{1-x}Co_xFe_2O_4$ could be qualitatively explained using the site distribution and the spin magnetic moment of substituted ions. The saturation magnetization and coercivity of the $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$ (x = 0.4) ferrite powders were also compared with pure $MnFe_2O_4$.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.275-280
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• 1995

The sites for $Fe^{+3}$ are partly substituted by $Co^{+2}$ and $Ti^{+4}$ cations to control coercivity of Ba-ferrite particles for use in high density magnetic recording. The substituted $Co^{+2}$ cation has very much different effects on magnetic properties and particle characteristics from that $Ti^{+4}$ cation has. The decrease in the coercivity with the $Co^{+2}$ substitution is attributed to the formation of excessive spinel-block(S-block) in pure Ba-ferrite crystal, while saturation magnetization is increased and the distributions of coercivity and particle size become broad. The substitution with the $Ti^{+4}$ decreases the sauration magnetization, but has less effect on a change in coercivity than the $Co^{+2}$. The $Ti^{+4}$ acts as a nucleation agent in amorphous phase of formulated compound, and consequently particle size and aspect ratio are decreased. Furthermore, the enhancement of substitution of the $Co^{+2}$ for the $Fe^{+3}$ sites in rhombohedral-block(R-block) by the $Ti^{+4}$ retards the nucleation of spinel phase of Ba-ferrite, which results in uniform magnetic properties of Ba-ferrite particles. It is suggested that the contents of the cations to be substituted for the $Fe^{+3}$ sites are optimized on the bases of magnetic properties and particle characteristics rather than on the base of electrical charge balance.

• Journal of the Korean Magnetics Society
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• v.5 no.2
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• pp.123-127
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• 1995

$CuFe_{2}O_{4}$ was accomplished by chemical rrethod and the crystallographic and magnetic properties have been studied by $M\"{o}ssbauer$ spectroscopy and X-ray diffraction. The slowly cooled sample is found to have a tetragonal spinel structure with the lattice constant $a=8.26{\pm}0.05{\AA},\;c=8.75{{\pm}}0.05{\AA}$. The $M\"{o}ssbauer$ spectra between the room temperature to the Curie temperature show that the $Cu_{2+}$ ions at octahedral site have the Jahn-Teller effect and the sample exhibits a structural phase transition near 630K due to the Jahn-Teller effect. The Curie temperature is found to be 690K and it is lower than that of ceramic method.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.186-190
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• 2005

The $Al_{0.2}CoFe_{1.8}O_4$ ferrite films and powders were prepared by the sol-gel method. The crystallographic and magnetic properties of the samples were examined with annealing temperature by X-ray diffraction, $M\ddot{o}ssbauer$ spetroscopy and vibrating sample magnetometry. The powder samples showed the presence of spinel structure at annealing temperatures above 673 K, while the film samples indicated the spinel structure above 873 K, also the particle size increased with rising annealing temperatures. The $M\ddot{o}ssbauer$ spectra of $Al_{0.2}CoFe_{1.8}O_4$ powder annealed above 873 K could be fitted as the superposition of two Zeeman sextets due to ferrimagnetic phase. And the spectra of annealed at 673 K exhibited the superposition of ferrimanetic and paramagnetic phase and those of annealed at 473 K showed only a paramagnetic phase. The magnetic behaviour of powders appeared that the coercivity increased until annealed at 673 K but decreased above this temperature. The coercivity of the film samples decreased from 1.084 kOe at 873 K to 0.540 kOe at 1073 K with increasing annealing temperatures.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.231-236
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• 2003

The $Al_{0.2}$CoF $e_{1.8}$ $O_4$ferrite powders have been prepared by the sol-gel method. The crystallographic and magnetic properties of the sample depending on annealing temperature have been investigated by means of x-ray diffraction, FE SEM, Mossbauer spetroscopy and vibrating sample magnetometry. The x-ray diffractions of all samples annealing temperature above 873 K clearly indicate the presence of spinel structure, the lattice constant decrease from 8.425 $\AA$ at 873 K to 8.321 $\AA$ at 1073 K, whereas the particle size rapidly increase from about 39 nm at 673 K to about 108 nm at 1073 K. The Mossbauer spectra annealed above 873 K could be fitted as the superposition of two sextets due to F $e^{3+}$ at A-site and B-site. The isomer shift (IS) and quadruple splitting (QS) values nearly constant with annealing temperature, whereas magnetic hyperfine field ( $H_{hf}$) of A-site slowly in crease and that of B-site fastly increases with increasing annealing temperature. The magnetic behaviour of powders shows that the saturation magnetization increase from 0.7 emu/g at 473 K to 72.1 emu/g at 1073 K while the coercivity decrease from 0.951 kOe at 673 K to 0.374 kOe at 1073 K with increasing annealing temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.8
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• pp.652-657
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• 1998

We have performed spin-spray ferrite plating of $Fe{_3}{-X}-Ni_XO_4$(X=0.17~0.26) films in the temperature region $T=80~95[^{\circ}C]$. A reaction solution and an oxidizing solution were supplied to a reaction chamber by supply pump. The solubility limit of Ni increases as the substrate temperature increase, from X=0.17 at $80[^{\circ}C]$ to X=0.26 at $95[^{\circ}C]$. All the films are polycrystalline with no preferential orientation, and the magnetization exhibits no definite anisotropy. Grain size in the films increases as X increases, reaching $0.87[\mu{m}]$ at X=0.26.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.90-95
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• 2000

The ferrites, CuFe2O4 and SrFe12O129, were applied to decompose H2O for H2 generation. The ferrites prepared by the coprecipitation were reduced by CH4 gas to make the oxygen deficient ferrite. H2O was decomposed to form H2 by the oxygen deficient iron oxide, and the decomposition reactions were accelerated by the addition of divalent metals such as Cu and Sr in the ferrites. The spinel type CuFe2O4 containing a relatively large amount of divalent metals was more effective to H2 generation than magnetoplumbite type SrFe12O19 in H2O decomposition.