• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.244-248
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• 1994

Magnetic and Magneto-optical characteristics of NdTbFeCo alloy films and NdTbFeCo/TbFeCo double-layered films have been investigated. It was observed that the Kerr rotation(${\theta}_{k}$) in the short wavelength region increased and the coercivity decreased as the substitutional amount of Nd for Tb in NdTbFeCo film at the constant FeCo content. In spite of the increased ${\theta}_{k}$, a small coercivity of NdTbFeCo film made this medium unsuitable for magneto-optical recording medium at short wavelength. An effort was made to improve coercivity by exchange coupling with TbFeCo film of high coercivity. In the exchange-coupled $Nd_{16.9}Tb_{15.2}Fe_{50.4}Co_{17.5}(150\;{\AA})/Tb_{21.1}Fe_{65.0}Co_{13.9}(300\;{\AA})$ double-layered film, the magnetization reversal switching field and the Kerr rotation angle were increased to about 6.0 KOe and $0.32^{\circ}$ at 500 nm, respectively. This result indicates that exchange-coupled NdTbFeCo/TbFeCo film can be a promising candidate for agneta-optical rerding medium short wavelenhth.

• Journal of Magnetics
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• v.8 no.4
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• pp.138-141
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• 2003

$Ni_{0.65}Zn_{0.35}Fe_2O_4$thin films were prepared by using a sol-gel method. Their crystallographic, dielectric and magnetic properties were investigated as a function of Cu contents by means of an X-ray diffractometer (XRD), X-ray reflectivity, LCZ meter (NF2232), a vibrating sample magnetometer (VSM), and an atomic force microscope (AFM). From typical C-V measurements for $Ni_{0.65}Zn_{0.35}Fe_2O_4$ thin films on p-type silicon substrate, the surface charge density was calculated as 1.4 ${\mu}$C/$m^2$. The dielectric constant evaluated from the capacitance at the accumulation state was 28. The high $H_{c}$ and low $M_{sat}$ at x=0.0 and 0.1 were due to the growth of the ${\alpha}$-$Fe_2O_3$ phase having antiferromagnetic properties. The rapidly decreased $H_{c}$ and increased $M_{sat}$ at x=0.2 and 0.3 can be explained that the ${\alpha}$-$Fe_2O_3$ phases have completely disappeared at x=0.3 and so, non-magnetic defects are minimized. The $M_{sat}$ was slightly decreased and the $H_{c}$ was increased above at x=0.3 because the increase of grain boundary due to smaller grain size acts as defects during magnetization process.

• Proceedings of the Korean Magnestics Society Conference
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• 1999.04a
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• pp.64-65
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• 1999

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.64-65
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• 1995

• Journal of Magnetics
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• v.6 no.4
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• pp.122-125
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• 2001

Phase relationships of the HDDR (hydrogenation, disproportionation, desorption and recombination)-treated Sm$_3$(Fe,M)$_{29}$-type alloy with chemical composition of Sm$_{9}$Fe$_{65}$ $Co_{20}$V$_{6}$ were studied by X-ray diffraction (XRD) and by thermomagnetic analysis (TMA). The alloy was disproportionated into a mixture of $SmH_{x}$ and $\alpha$-Fe at high temperature under hydrogen gas. The disproportionated material was recombined into a mixture of Sm-(Fe,M) (M = Co and/or V) and $\alpha$-Fe phases. The structure of the Sm-(Fe,M) phase was dependent upon the recombination conditions, and a detailed phase diagram showing the phase relationships in the HDDR-treated alloy has been established. The Sm-(Fe,M) phase in material recombined above $900^{\circ}C$ had the $Sm_2Fe_{17}$-type structure, and it exhibited the $SmFe_{7}$-type structure when recombined at temperatures ranging from $700^{\circ}C$ to $850^{\circ}C$. Recombination below $650^{\circ}C$ led to the $SmFe_3$-type structure of the Sm-(Fe,M) phase. Curie temperatures of the Sm-(Fe,M) phases in the recombined material were significantly higher than those of the corresponding stoichiometric phases. It was suggested that the chemical composition of the Sm-(Fe,M) phases may be significantly different from that of the corresponding stoichiometric phases. All the HDDR-treated $Sm_{9}Fe_{65}Co_{20}V_{6}$ materials showed the soft magnetic features regardless of the phase constitution.n.

• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.7-12
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• 1997

Amorphous $Fe_{50}Zr_{50}$ alloy has been manufactured by mechanical alloying from pure elemental powders of Fe and Zr in conventional ball mill under an Ar atmosphere. Structure and magnetic properties of the amorphous phase were studied by transmission electron microscopy and SQUID magnetometry. Selected area diffraction patterns taken from the mechanically alloyed powders showed two halo rings, indicating coexistence of Fe rich and Zr rich amorphous phases in mechanically alloyed powder. Curie temperature of the Fe rich amorphous phase, measured by Arrot plot, was 195 K. Fe content in the ferromagnetic amorphous phase, estimated from the Curie temperature, was about 65 at%. Spin wave stiffness constant of $Fe_{50} Zr_{50}$ alloys processed for 100 and 200 hrs were 52.2 and 63.8 meV, respectively. The higher spin wave stiffness constant in 200 hrs milled powders may arise from the precipitation of $\alpha$-Fe by partial crystallization of amorphous phase.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.65-71
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• 2010

In this study, the effect of Sn and Mg on microstructure and mechanical properties of Cu-Fe-P alloy were investigated by using scanning electron microscope, transmission electron microscope, tensile strength, electrical conductivity, thermal softening, size and distribution of the precipitation phases in order to satisfy characteristic for lead frame material. It was observed that Cu-0.14wt%Fe-0.03wt%P-0.05wt%Si-0.1wt%Zn with Sn and Mg indicates increasing tensile strength compare with PMC90 since Sn restrained the growth of the Fe-P precipitation phase on the matrix. However, the electrical conductivity was decreased by adding addition of Sn and Mg because Sn was dispersed on the matrix and restrained the growth of the Fe-P precipitation. The size of 100 nm $Mg_3P_2$ precipitation phase was observed having lattice parameter $a:12.01{\AA}$ such that [111] zone axis. According to the results of the study, the tensile strength and the electrical conductivity satisfied the requirements of lead frame; so, there is the possibility of application as a substitution material for lead frame of Cu alloy.

• Journal of Magnetics
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• v.19 no.1
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• pp.55-58
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• 2014

We have synthesized ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}/{\alpha}$-phase $Fe_{65}Co_{35}$ composite by annealing a mixture of paramagnetic ${\varepsilon}$-phase $Mn_{54}Al_{46}$ and ferromagnetic ${\alpha}$-phase $Fe_{65}Co_{35}$ particles at $650^{\circ}C$. The volume fraction ($f_h$) of hard ${\tau}$-phase $Mn_{54}Al_{46}$ of the composite was varied from 0 to 1. During the annealing, magnetic phase transformation occurred from paramagnetic ${\varepsilon}$-phase to ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}$. The magnetization and coercivity of the composite monotonically decreased and increased, respectively, as the $f_h$ increased. These results are in good agreement with our proposed composition dependent coercivity and modified magnetization equations.

• Proceedings of the Korean Magnestics Society Conference
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• 1995.10a
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• pp.64-65
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• 1995

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.85-92
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• 1993

Large single crystals of olivine were grown by using image furnace(floating zone furnace)under controlled partial pressure of oxygen. The transparent crystals have maximum sizes 65mm in length by 7mm in diameter. When partial pressure of oxygen was decreased, the portion of secondary phases in crystals were increased so that it made crystals dark brown. The secondary phases were proved to be solid solution of Mg, Si, and Fe by electron microprobe analysis. Mg was major portion and the rest was minor.