• Progress in Superconductivity
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• v.14 no.2
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• pp.110-115
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• 2012

Samples with nominal compositions of $RuSr_2(Eu_{1.34-x}Tb_xCe_{0.66})Cu_2O_z$ (x = 0, 0.67) were prepared and their superconductivity and magnetic properties were compared to shed light on the effect of Tb substitution for Eu. X-ray diffraction measurements indicate that the Tb substitution resulted in a decrease in both a and c lattice parameters in consistent with ionic size difference between Eu and Tb. Contrary to the Tb-free sample, no superconducting transition behavior is observed in the Tb-sustituted sample. It is also found that the Tb substitution for Eu significantly increases the weak-ferromagnetic component of the field-cooled magnetic susceptibility as well as an increase in the magnetic ordering temperature. These results suggest that the magnetic state of the Ru sublattice is significantly affected by the Tb substitution for Eu.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.55-59
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• 1991

The temperature-dependent magnetization curves of amorphous Fe-Co-(Nd, Sm, Gd, Tb)-B alloys were measured using a vibrating sample magnetometer from 77 K up to 900 K. The spin wave stiffness constants and the range of the exchange interaction were calculated from the saturation magnetization values at 0 K. Curie temperatures and the Bloch coefficients estimated from the saturation magnetization curves. The low temperature dependence of magnetization is in good agreement with Bloch relation, $M_{s}(T)=M_{s}(O)(1-BT^{3/2}-CT^{5/2})$. The spin wave stiffness constant and the range of exchange interaction are decreased by substitution of heavy rare earth (Tb, Gd).

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.245-248
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• 2006

[ $Tb_{3-x}Bi_xFe_5O_{12}$ ] has been studied by x-ray diffraction (XRD), vibrating sample magnetometer, $M\"{o}ssbauer$ spectroscopy. The crystal structures were found to be a cubic garnet structure with space group Ia3d. The lattice constants increase linearly with increasing bismuth concentration. With increase of bismuth substitution, the $N\'{e}el$ temperature increases but the compensation temperature decreases. We have observed the negative magnetization in Bi-TbIG system which has not been reported in garnet systems. $M\"{o}ssbauer$ spectra were measured at various temperatures from 4.2 K to $N\'{e}el$ temperature. The isomer shifts at room temperature are ${\sim}0.26mm/s$ which is consistent with ferric state.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.594-597
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• 1999

The new green and red phosphors for PDP application activated by T $b^{3+}$ and E $u^{3+}$ were synthesized, and their photoluminance properties were investigated. It was found that the brightness of $Al_3$Gd $B_4$ $O_{12}$ :T $b^{3+}$ green phosphor under 147nm VUV irradiation was higher than that of commercial Z $n_2$ $SiO_4$:M $n^{2+}$ phosphor. But the emitting intensity of A1$_3$Gd $B_4$ $O^{12}$ :E $u^{3+}$ red phosphor was inferior to the commercial (Y,Gd)B $O_3$:E $u^{3+}$. $Al_3$Gd $B_4$ $O_{12}$ Phosphor had a strong excitation band at 160nm associated with the host absorption, and also the photoluminance excitation intensity of $Al_3$Gd $B_4$ $O_{12}$ :T $b^{3+}$ was higher than that of Z $n_2$ $SiO_4$:M $n^{2+}$, but the intensity of $Al_3$Gd $B_4$ $O_{12}$ :E $u^{3+}$ phosphor was smaller than (Y,Gd)B $O_3$:E $u^{3+}$ phosphor In the VUV range. C $e^{3+}$ co-doping in A1$_3$Gd $B_4$ $O^{12}$ :E $u^{3+}$ and substitution of $Al^{3+}$ by G $a^{3+}$ A1$_3$Gd $B_4$ $O^{12}$ :E $u^{3+}$ phosphor were tried, but they did not improved the optical property .d the optical property .ty .

• Journal of Magnetics
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• v.6 no.2
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• pp.57-60
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• 2001

Mechanically alloyed $TbCu_7 -type \;Sm_{12.5}Fe_{87.5-x}Ti_x$(x=0, 2.5, 5, 7.5),and their nitrides have been studied systematically by X-ray diffraction, A.C. initial susceptibility, and pulsed magnetization measurement. In this series, the volume expansion by nitriding is 5.6%~7.3%, and the increment of the Curie temperature is in the range of 21$0^{\circ}C$~35$0^{\circ}C$. With increasing Ti content, the remanence decreases linearly due to the substitution of non-magnetic Ti, and the coercivity decreases rapidly from 34.6 kA/cm (43.5 kOe) for $\chi$=0 to 14.3 kA/cm (18 kOe) for $\chi$=7.5. In the $Sm_{12.5}Fe_{87.5-x}Ti_xN_y$ series, the best magnetic properties were obtained from .7Ti7Ny series, the best magnetic properties were obtained from $Sm_{12.5}Fe_{87.5}N_y$($\chi$=0) with $_iH_c$=34.6 kA/cm (43.5 kOe), $B_r=0.75 \;T, \;and (BH)_{max}=113.8 kJ/m^3$(10.9 MGOe).

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.683-686
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• 1995

Using by the x-ray diffractometry(XRD), the thermomagnetic analysis(TMA), a scanning electron microscopy (SEM-EDX), we knew that the $(Sm_{0.5}RE_{0.5})Fe_{11}Ti$ (RE=Ce,Pr,Nd,Sm,Gd,Tb) compounds were formed to tetragonal $ThMn_{12}$-type structure having a uniaxial magnetocrystalline anisotropy with easy magnetization c-axis. The intrinsic magnetic properties of those were determined by fitting the two magnetization curves of experimental and calculation magnetization. The anisotropy constant $K_{1}$ of this compounds was in the range of $1.75\;-\;9.2\;MJ/m^{3}$ and approximately one order higher than $K_{2}$. $SmFe_{11}Ti$ had the highest anisotropy of $K_{1}\;=\;9.2\;MJ/m^{3}$, $K_{2}\;=\;0.4\;MJ/m^{3}$ and ${\mu}_{o}H_{A}=\;19.8\;T$ among the compounds, substitution of any other rare earth elements for Sm decreased magnetocrystalline anisotropy.

• Tuberculosis and Respiratory Diseases
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• v.63 no.2
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• pp.128-138
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• 2007

Backgrounds: Mutations of katG and inhA (ORF and promoter) are known to be related to isoniazid (INH) resistance of Mycobacterium tuberculosis. Because reports on these mutations in Korean isolates are limited (i.e. only the frequency of katG codon 463 was evaluated.), we tried to know the kinds of mutations of two genes and their frequencies in INH resistant Korean M. tuberculosis strains. Methods: PCR was performed to amplify katG (2,223 bp), inhA ORF (-77~897, 975 bp), and inhA promoter (-168~80, 248 bp) from 29 multidrug resistant M. tuberculosis (MDR-TB) DNAs prepared by bead beater-phenol method. Their sequences were determined and analyzed by ABI PRISM 3730 XL Analyzer and MegAlign package program, respectively. Results: All of the isolates had more than one mutation in katG or inhA gene. Twenty seven (93%) of 29 tested strains had katG mutations, which suggests that katG is a critical gene determining INH resistance of M. tuberculosis. Amino acid substitutions, such as Arg463Leu and Ser315Thr, due to point mutations of the katG were the most frequent (62.1% and 55.2%) mutations. In addition, deletion of the katG gene was frequently observed (17.2%). Analyzed Korean MDR-TB isolates also had variable inhA mutations. Point mutation of inhA promoter region, such as -15 ($C{\rightarrow}T$) was frequently found. Substitution of amino acid (Lsy8Asn) due to point mutation ($AAA{\rightarrow}AAC$) of inhA ORF was found in 1 isolate. Interestingly, 14 point mutated types that were not previously reported were newly found. While four types resulted in amino acid change, the others were silent mutations. Conclusions: Although it is not clear that the relationship of these newly found mutations with INH resistance, they show marked diversity in Korean MDR-TB strains. It also suggests their feasibility as a molecular target to supplement determining the INH resistance of clinical isolates because of the possible existence of low-level INH resistant strains.