• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.2
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• pp.80-84
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• 2015

Mn-Co-Ni oxide system has been used as the NTC thermistors for normal temperature applications. Mn-Co-Ni oxide-based thermistors were sintered at different temperatures for a constant processing time from 900 to $1300^{\circ}C$ for 3 h. The crystal structure, bulk density, microstructure and chemical composition were characterized by XRD, FE-SEM and WD-XRF. The plot of the resistance versus measuring temperature was characterized for the sintered sample at the $1250^{\circ}C$. Moreover, the relationship between log resistivity and reciprocal of absolute temperature of the NTC thermistor was investigated.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.196-202
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• 2000

Top synthetic spin valves with structure Ta/NiFe/CoFe/Cu/CoFe(P1)/Ru/CoFe(P2)/FeMn/Ta on Si(100) substrate with natural oxide were prepared by dc magnetron sputtering system, and investigated on the magnetoresistance properties and effective exchange bias field. As the thickness of FeMn increased above 150 $\AA$, MR ratio was decreased due to the current shunting effect. As the thickness of free layer decreased below 40$\AA$, MR ratio was reduced rapidly. In case of 40 $\AA$ thick of free layer, spin valve film with a structure Si(100)/Ta(50 $\AA$)/NiFe(27 $\AA$)/CoFe(13 $\AA$)/Cu(26 $\AA$)/CoFe(30 $\AA$)/Ru(7 $\AA$)/CoFe(15 $\AA$)/FeMn(100 $\AA$)/Ta(50 $\AA$) exhibited maximum MR ratio of 7.5 % and an effective exchange bias field of 600 Oe, respectively. Thickness difference dependence in this synthetic spin valve structure on effective exchange field was investigated and interpreted by the analytical method. It should be noted that thickness increase of CoFe(P 1) and decrease of CoFe(P2) in synthetic antiferromagnet leaded to the decrease in effective exchange bias field by experimentally and analytically.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.225-229
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• 2015

This study was performed to investigate crystal structure of cubic spinel-type monophase oxide composed of the Mn-Co-Ni ternary system. Starting material was prepared by mixing Mn, Co, Ni oxides then evaporation to dryness. The XRD patterns were analyzed by in-situ XRD as increasing temperature from room temperature to $1400^{\circ}C$ in air atmosphere. The cubic spinel phase was existed in a temperature range from $900^{\circ}C$. However, separation of NiO phase was detected from $1300^{\circ}C$, which was the origin of deterioration in the crytallinity. The surface morphology of the manufactured NTC thermistors were analyzed by FE-SEM for comparison of good and bad samples.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.203-209
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• 2000

Top synthetic spin valves with structure Ta/NiFe/CoFe/Cu/CoFe(P 1)/Ru/CoFe(P2)/FeMn/Ta on Si (100) substrate with natural oxide were prepared by dc magnetron sputtering system. We have changed only the thickness in free layers and the thickness difference (Pl-P2) in two ferromagnetic layers separated by Ru, and investigated the effect of magnetic film thickness on interlayer coupling field in spin valve with synthetic antiferromagnet. According to the decrease of free layer thickness, interlayer coupling field was increased due to the magnetostatic coupling(orange peel coupling). In case of t$\_$P1/>t$\^$P2/, interlayer coupling field agreed well with the modified Neel model suggested in conventional spin valve structures by Kools et al. However, in case of t$\_$P1/>t$\^$P2/, it was found that the interlayer coupling field was not explained by the Modified Neel Model and was confirmed the necessity of further remodeling. The dependence of Cu thickness on the interlayer coupling field was investigated and 10 Oe of interlayer coupling field was obtained when the Cu thickness is 32 $\AA$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.850-854
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• 2011

Nano-fibers of the $Li[Ni_{1/3}Co_{1/3}Mn_{1/3}]O_2$ electrode were synthesized from a metal oxide precursor using the electrospun method. The XRD patterns of all prepared powders showed a hexagonal ${\alpha}$ - $NaFeO_2$ structure (space group: R-3 m, 166). Scanning electron microscopy showed that all the synthesized samples were comprised of nanofibers with a size of 100~800 nm. Among the samples tested, the calcined $Li[Ni_{1/3}Co_{1/3}Mn_{1/3}]O_2$ nanowires in oxygen heating atmosphere showed a high charge and discharge capacity of 239.22 and 172.81 $mAhg^{-1}$ at the $1^{st}$ cycle, respectively. In addition, the charge transfer resistance was also improved significantly compared to the other samples.

• Ocean and Polar Research
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• v.26 no.2
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• pp.231-243
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• 2004

Sequential extraction was carried out on twenty two subsamples of three ferromanganese crusts from three seamounts (Lemkein, Lomilik, and Litakpooki) near the Marshall Islands in the western Pacific. The extraction was designed to fractionate Fe-Mn crust forming elements into low defined groups: (1) exchangeable and carbornate, (2) Mn-oxide, (3) Fe-oxyhyd.oxide, and (4) residual fraction. X-ray diffraction result shows that target material were well removed by each extraction step except for CFA in phosphatized crusts generation. According to chemical analysis of each leachate, most of elements in the Fe-Mn crusts are bound with two major phases. Mn, Ba, Co, Ni, Zn, (Fe, Sr, Cu, and V) are strongly bounded with Mn-oxide $({\delta}-MnO_2)$ phase, whereas Fe, Ti, Zr, Mo, Pb, Al, Cu,(V, P, and Zn) show chemical affinity with Fe-oxyhydroxide phase. This result indicates that significant amount of Al, Ti, and Zr can not be explained by detrital origin. Ca, Mg, K, and Sr mainly occur as exchangeable elements and/or carbonate phase. Outermost layer 1 and inner layer 2 which are both young crusts generations are similar in chemical speciations of elements. However, some of Fe-oxyhydroxide bounded elements (Pb, Y, Mo, Ba, Al, and V) in phosphatized innermost layer 3 are released during phosphatization and incorporated into phosphate (Pb, Y, Mo, and Ba) or Mn-oxide phase (Al and V). Our sequential extraction results reveal that chemical speciations of elements in the hydrogenetic crusts are more or less different from interelemental relationship calculated by statistical method based on bulk chemistry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.361-365
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• 2017

In this paper, we investigated the effect of Co content on the microstructural and electrical properties of $Ni_{0.79}Mn_{2.21-x}Co_xO_4$ (x=0 to 0.25) specimens. Solid-state reaction was used to prepare the bulk specimens. XRD (X-ray diffraction) patterns showed that all compositions had a cubic spinel phase. As a result of the microstructural properties, FE-SEM(field-emission scanning electron microscopy) analysis showed a dense structure, and the mean grain size increased from $5.24{\mu}m$ to $7.33{\mu}m$ with an increase of Co content from x=0 to 0.25. All specimens exhibited the typical NTC thermistor characteristics as the electrical resistance exponentially decreased with increasing temperature. The resistivity and the B-value of $Ni_{0.79}Mn_{1.96}Co_{0.25}O_4$ were $2959{\Omega}{\cdot}cm$ and 3719, respectively.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.315-320
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• 1989

A method was presented for the analysis of trace metals in iron oxide ore. The method utilized ammonium pyrrolidinedithiocarbamate (APDC)-methyl isobutyl ketone (MIBK) extraction procedure and analysis by atomic absorption spectroscopy (AA). Citrate at pH $8{\sim}10$ for the determination of Co, Ni and Cu or tiron at pH $6{\sim}7$for the determination of Mn and Cu was added as a masking agent to prevent extraction of Fe(III) into the organic phase. Reduction of solubility of MIBK in water was achieved by addition of NaCl as a salting-out agent. Back extraction of the MIBK extracts with aqueous $HNO_3$ was also studied to increase the stability of metal extracts.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.236-239
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• 2004

We studied the specular spin valve (SSV) having the spin filter layer (SFL) in contact with the ultrathin free layer composed of Ta3/NiFe2/IrMn7/CoFel/(NOLl)/CoFe2/Cu1.8/CoFe( $t_{F}$)/Cu( $t_{SF}$ )/(NOL2)/Ta3.5 (in nm) by the magnetron sputtering system. For this antiferromagnetic I $r_{22}$M $n_{78}$-pinned spin filter specular spin valve (SFSSV) films, an optimal magnetoresistance (MR) ratio of 11.9% was obtained when both the free layer thickness ( $t_{F}$) and the SFL thickness ( $t_{SF}$ ) were 1.5 nm, and the MR ratio higher than 11% was maintained even when the $t_{F}$ was reduced to 1.0 nm. It was due to increase of specular electron by the nano-oxide layer (NOL) and of current shunting through the SFL. Moreover, the interlayer coupling field ( $H_{int}$) between free layer and pinned layer could be explained by considering the RKKY and magnetostatic coupling. The coercivity of the free layer ( $H_{cf}$ ) was significantly reduced as compared to the traditional spin valve (TSV), and was remained as low as 4 Oe when the $t_{F}$ varied from 1 nm to 4 urn. It was found that the SFL made it possible to reduce the free layer thickness and enhance the MR ratio without degrading the soft magnetic property of the free layer.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.82-82
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• 2008