• Analytical Science and Technology
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• v.11 no.3
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• pp.202-205
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• 1998

X-ray absorption fine structure spectroscopic studies at the Ni K-edge have been performed for the Ni-Zn alloy coating layer on steel. The Ni-Zn interatomic distances and Debye-Waller factors were determined by fitting the experimental data with the theoretical spectra in the temperature range of 80 to 300K. The average Ni-Zn interatomic distance was found to be $2.557{\AA}$ and the variation of the Ni-Zn interatomic distance with temperature in this range was insignificant. From the comparison of the Ni-Zn interatomic distance with the nearest neighbor distance of pure Zn lattice it has been suggested that there is an apparent contraction around Ni atom.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.219-223
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• 2004

L $i_{0.5}$F $e_{2.5-{\chi}}$R $h_{\chi}$ $O_4$ ($\chi$ = 0.25, 0.50, 0.75, 1.00) has been prepared by solid state reaction. Crystallographic and magnetic properties were investigated by Mossbauer spectroscopy, SQUID magnetometry, and x-ray diffraction. The crystal structure is found to be a cubic spinel structure with space group Fd3m for all the samples. The lattice constant $a_{0}$ increases from 8.3365 $\AA$ to 8.3932 $\AA$ with increasing Rh concentration $\chi$. The migration of Li ion has been confirmed by x-ray patterns and the results of applied field Mossbauer analysis. The temperature dependence of the absorption area of each site was analyzed with the Debye model for the recoil-free fraction. The Debye temperature for the octahedral sites is almost as large as for the tetrahedral sites, thereby suggesting similar inter-atomic binding forces for the octahedral and the tetrahedral sites. The saturated magnetic moment and the Mossbauer spectra taken at 4.2 K under the applied field (6 T) show that the spin structure of L $i_{0.5}$F $e_{2.5-{\chi}}$R $h_{\chi}$ $O_4$ is compatible with the collinear Neel Model.

• Korean Journal of Materials Research
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• v.6 no.3
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• pp.305-308
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• 1996

YxFe2-xO3(x=0.82)의 결정상 변환을 상온에서의 x선회절과 온도구간 80-541K에서의 Mossbauer 분광 방법에 의해서 연구하였다. Xtjs 회절선은 시료가 orthorhombic 결정상과 garnet 결정상이 공존하고 있으며, 공존비는 실험오차 범위내에서 garnet 구조가 orthorhombic 구조보다 우세함을 보인다. 공존상중에서 garnet 구조의 자기상 변환온도는 536$\pm$5 K로 결정하였다. Debye 모형을 이용한 Mossbauer 스펙트럼의 recoil-free fration 분석결과는 garnet 결정상내의 d자리나 a자리에 vacancy의 존재 가능성을 시사한다. 부가적으로 시료가 포함하는 각 결정상의 Debye 특성온도를 결정하였다.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.293-297
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• 1992

The magnetic properties of the amorphous Fe/sub 32/Ni/sub 36/Cr/sub 14/P/sub 12/B/sub 6/ has been studied by Mossbauer spectroscopy in the temperature range of 88-400K. The analysis of the spectrum of B8K, the magnetic hyperfine field and quadrupole splitting are found to be 140.5kOe and almost zero, which means that the magnetic hyperfine field is randomly oriented with respect to the principal axes of the electric field gradient, respectively. The values of quadrupole splitting in paramagnetic phase with Tc=280K are independent on the changes of temperature. Debye temperature is found to be about 288k from the analysis of recoilless fraction.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1107-1112
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• 1996

Ni를 Cd로 대치시켜 세라믹 소결법으로 합성한 Ni0.8Cd0.2Fe2O4 의 X-ray 회절선을 측정하여 구조를 확인하고, 형성된 결정체의 격자 상수를 조사하였다. 이 시료의 Mossbauer 스펙트럼을 80K-900K의 온도 영역에서 측정 분석하여 Mossbauer parameter의 온도 의존성과 Fe 이온에 대한 자료를 얻고, 이 자료를 토대로 Ni0.8Cd0.2Fe2O4 의 자기 전이 현상과 Curied 온도 Tc와 격자 비열 및 Debye 온도와 같은 물성을 조사하였다.

• Journal of Hydrogen and New Energy
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• v.6 no.1
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• pp.17-22
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• 1995

Thermally evaporated Pd films on substrate were hydrogenated upto 1 bar of hydrogen gas at room temperature. Temperature dependence hange of electrical resistivity on Pd films is examined in the thickness range between $60{\AA}$ and $990{\AA}$. Resistivity of Pd is fitted well with Bloch-$Gr{\ddot{u}}neisen$ formula. Debye temperatures of Pd films are about 254 K, which are 20 K lower than that of bulk Pd. Debye temperature is not sensitive to film thickness change. Temperature of substrate during evaporation changes temperature dependence of resistivity of films much. Optical phonon contribution increases with decreasing temperature of PdHx.

• Journal of the Korean Magnetics Society
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• v.9 no.6
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• pp.271-277
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• 1999

Amorphous $Fe_{83}B_9Nb_7Cu_1$ alloy has been studied by M$\"{o}$ssbauer spectroscopy. Revised Vincze method was used and distributions of hyperfine field, isomer shift, and quadrupole line broadening of the sample at various temperatures have been evaluated and Curie temperature and $H_{hf}\;(0)$ were calculated to be 393 K and 231 kOe, respectively. Temperature variation of reduced average hyperfine field shows a flattered curvein comparison with the Brillouin curve for S=1. This behavior can be explained on the basis of Handrich molecular field model, in which the parameter Δ, which is a measure of fluctuation in exchange interactions, is assumed to have the temperature dependence ${Delta}=0.75-0.64{\tau}+0.47{\tau}^2$ where $\tau$ is $T/T_C$. At low temperature, the average hyperfine field can be fitted to $H_{hf}\;(T)=H_{hf}\;(0)\;[1-0.44\;(T/T_C)^{3/2}-0.28(T/T_C)^{5/2}-… ]$, which indicates the presence long wave length spin wave excitations. At temperature near TC, reduced average hyperfine field varies as $1.00\;[1-T/T_C]^{0.39}$. It is also found that half-width of the hyperfine field distribution was 102 kOe (3.29 mm/s) at 13 K and decreased monotonically as temperature increased. Above the Curie temperature, an average quadrupole splitting value of 0.43 mm/s was found. Average line broadening due to quadrupole splitting distribution was 0.31 mm/s at 13 K and decreases monotonically to 0.23 mm/s at 320 K, whereas that due to the isomer shift distribution is 0.1 mm/s at 13 K and 0.072 mm/s at 320 K, which is much smaller than that of both hyperfine field and quadrupole splitting. The temperature dependence of the isomer shift can be fitted within the harmonic approximation to a Deybe model with a Debye temperature ${Theta}_D=424{\pm}5K$.TEX>.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.28-33
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• 2006

La substituted perovskite $BiFeO_3$ have been prepared by a sol-gel method. Magnetic and structural properties of the powders were characterized with Mossbauer spectroscopy, XRD, SEM, and TG-DTA. The crystal structure is found to be a rhombohedrally distorted perovskite structure with the lattice constant $\alpha=3.985{\AA}\;and\;\alpha=89.5^{\circ}.\;Bi_{2/3}La_{1/3}FeO_3$ powders that were annealed at and above $600^{\circ}C$ have a single-phase perovskite structure. However, powders annealed at $900^{\circ}C$ have a typical perovskite structure with small amount of $Bi_2O_3$ phase. The Neel temperature of $Bi_{2/3}La_{1/3}FeO_3$ is found to be $680\pm3K$. The isomer shift value at room temperature is found to be 0.27 mm/s relative to the Fe metal, which is consistent with high-spin $Fe^{3+}$ charge states. Debye temperature far$Bi_{2/3}La_{1/3}FeO_3$ is found to be $305\pm5K$. The average hyperfine field $H_{hf}(T)$ of the $Bi_{2/3}La_{1/3}FeO_3$, shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.42(T/T_N)^{3/2}-0.13(T/T_N)^{5/2}$ for $T/T_N<0.7$ indicative of spin-wave excitation.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.18-19
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• 2002

$^{57}$ Fe화합물에 대한 Mossbauer 분광학 연구로부터 이들 자성물질의 이성핵적이동값, 전기사중극자 분열값 및 초미세자기장의 크기를 결정하였으며 이들값으로부터 Fe의 이온상태, 큐리온도, 각 Site의 점유율, Debye온도, spin wave상수, exchange integral을 계산하였다. $^{57}$ Co감마선을 사용하는 등가속도형 Mossbauer 분광기를 이용하여 4.2 K 부터 900 K 온도영역에서 실험을 하였다. (중략)

• Journal of the Korean Magnetics Society
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• v.7 no.2
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• pp.76-81
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• 1997

$Cu_{0.9}Ni_{0.1}Fe_2O_4$ has been studied with Mossbauer spectroscopy and X-ray diffraction. The crystal structure is found to be a cubic spinel with the lattice constant $a_0=8.386{\AA}$. The Curie temperature is determined to be $T_c=755K$ for a heating rate of 5 K/ min. The Mossbauer spectra consist of two six-line patterns corresponding to $Fe^{3+}$ at the tetrahedral(A) and octahedral(B) sites. Debye temperatures for A and B sites are found to be 568 k and 194 K, respectively. Atomic migration of $Cu_{0.9}Ni_{0.1}Fe_2O_4$ begins near 350 K and increases rapidly with increasing temperature such a degree that 71% of the ferric ions as A sites have moved over to the B sites at 550 K.