• Journal of the Korean Magnetics Society
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• v.21 no.3
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• pp.83-87
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• 2011

We have analyzed the torque signals measured in synthetic antiferromagnetic (SAF) coupled CoFeB/Ru/CoFeB thin film, which signals were drastically changed at flopping field ($H_F$) and saturation field ($H_s$). The minimum value of negative uniaxial anisotropy constant ($-\;K_1$) was appeared at HF. The $-\;K_1$ was due to the zero net magnetization by the antiferromagnetic coupling between two ferromagnetic layers. Whereas, the biaxial anisotropy constant (K2) was induced in the field range of $H_F$ < H < $H_s$. The induced $K_2$ was originated from deviation angles between magnetization directions of two ferromagnetic layers. And at H > $H_s$, intrinsic uniaxial anisotropy constant of CoFeB layer was observed. These change of the anisotropy constant with magnetic field was explained by the magnetization process of two ferromagnetic layers based on Stoner-Wohlfarth model calculation for SAF thin film.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.19-19
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• 2011

We studied the effect of Dy content on the magnetic properties of cobalt ferrite single crystal. The $CoFe_{1.9}Dy_{0.1}O_4$ single crystals were grown by the flux method by using $Na_2B_4O_{7.}10H_2O$ (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction test at room temperature confirmed the spinel cubic symmetry with lattice constant a = $8.42{\AA}$ of the single crystals. The presences of constitute elements (Co, Fe and Dy) was endorsedby EDAX analysis. The saturation magnetization (Ms) of $CoFe_{1.9}Dy_{0.1}O_4$ single crystals was measured and is found to be 72emu/g or equivalently $3.2{\mu}B$/f.u. at 300 K. The observed Ms and coercivity (Hc) is found to be lower than that of pure $CoFe_2O_4$.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.12a
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• pp.70-71
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.46-47
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• 2017

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.95-96
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• 2017

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.491-492
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• 2008

The effect of B on the hot ductility of Fe-29Ni-17Co Kovar alloy and the mechanism of high temperature deformation behavior were investigated. Hot-tensile test was carried out at the temperature range of $900^{\circ}C-1200^{\circ}C$. Optical microscopy and scanning electron microscopy were used to investigate the microstructure and fracture during hot deformation. The hot ductility of Kovar alloy was drastically increased with the addition of Boron. The improvement of hot ductility results from the grain boundary migration mainly due to the dynamic recrystallization at lower temperature range($900^{\circ}C$).

• Bulletin of the Korean Chemical Society
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• v.9 no.5
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• pp.283-288
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• 1988

The titled properties on reduction of the perovskite $LaBO_3$ (B = Fe, Co, Ni) have been investigated by means of temperature-programmed reduction, isothermal reduction and X-ray diffraction methods. Nominal composition of $LaFeO_{3.18},\;LaCoO_{3.00}\;and\;LaNiO_{2.92}$ are determined. Reduction reaction of these mixed oxides differed according to B-site transition metal and thermal stability on reduction decreased as following order: $LaFeO_{3.18}$ > $LaCoO_{3.00}$ > $LaNiO_{2.92}$. From the results of isothermal reaction, kinetics on reduction of the perovskite has been discussed in detail.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.912-918
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• 2002

Ni-Mn-Co-Fe oxide thick films were coated on an alumina substrate by screening printing technique. The microstructure and electrical properties of the thick films, as a function of composition and sintering temperature, were investigated. The components of the NTC thick films sintered at 1150${\circ}C$ were distributed homogeneously. On the other hand, in the case of the NTC thick films sintered at 1200 and 1250${\circ}C$, Co element was distributed homogeneously, but Ni, Mn and Fe elements were distributed heterogeneously, resulting in the formation of Ni rich and Mn-Fe rich regions. All the thick film NTC thermistors prepared showed a linear relationship between log resistance (log R) and the reciprocal of absolute temperature (1/T), indicative of NTC characteristics. At a given NiO and $Mn_3O_4$ content, the resistance, B constant and activation energy of $(Ni_{1.0}Mn_{1.0}Co_{1-x}Fe_x)O_4$ (0.25${\le}$x${\le}$0.75) and $(Ni_{0.75}Mn_{1.25}Co_{1-x}Fe_x)O_4$ (0.25${\le}$x${\le}$0.75) thermistors increased with increasing $Fe_2O_3$ content.

• Journal of Magnetics
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• v.18 no.4
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• pp.395-399
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• 2013

The metallic glass ribbons of $[(Fe_xCo_{1-x})_{0.75}B_{0.2}Si_{0.05}]_{96}Mo_4$ (x = 0, 0.3, 0.6, 0.9 at.%) and $[(Fe_xCo_{1-x})_{0.75}B_{0.2}Si_{0.05}]_{96}Nb_4$ (x = 0, 0.3, 0.6, 0.9 at.%) were obtained by melt spinning with 25-30 ${\mu}m$ thickness. The thermal stability, mechanical properties and magnetic properties of Fe-Co-B-Si based systems were investigated. The values of thermal stability were measured using differential scanning calorimetry (DSC), including glass transition temperature ($T_g$), crystallization temperature ($T_x$) and supercooled liquid region (${\Delta}T_x=T_x-T_g$). These amorphous ribbons were identified as fully amorphous, using X-ray diffraction (XRD). The mechanical properties of Febased samples were measured by nano-indentation. Magnetic properties of the amorphous ribbons were measured by a vibrating sample magnetometer (VSM). The amorphous ribbons of $[(Fe_xCo_{1-x})_{0.75}B_{0.2}Si_{0.05}]_{96}Mo_4$ (x = 0, 0.3, 0.6, 0.9 at.%) and $[(Fe_xCo_{1-x})_{0.75}B_{0.2}Si_{0.05}]_{96}Nb_4$ (x = 0, 0.3, 0.6, 0.9 at.%) exhibited soft magnetic properties with low coercive force ($H_c$) and high saturation magnetization (Ms).

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.166-166
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• 2003