Mg_1-xZn_xFeAlO₄의 결정학적 구조 및 자기적 성질

고정대,홍성락,Ko Jeong-Dae,Hong Sung-Rak 한국재료학회 2005 한국재료학회지 Vol.15 No.6

The crystal structure and magnetic properties of the $Mg_{1-x}Zn_xFeAlO_4\;(0{\leq}x\leq1.0)$ have been investigated by means of x-ray diffractometry and $M\ddot{o}ssbauer$ spectroscopy. The samples$(0{\leq}x\leq1.0)$ have been prepared by the ceramic sintering method. The x-ray diffraction pattern shows that the crystal structure of the samples is a cubic spinel type. The lattice constant has been found by extrapolation using the Nelson-Riley function and it increases slightly from $8.3496\AA\;to\;8.4128\AA$ with Zn concentration. The $M\ddot{o}ssbauer$ spectra for x<0.4 show a superposition of two sextets ana a paramagnetic doublet at room temperature. The superparamagnetic doublet for x<0.4 seems to be due to Al ion in tetrahedral site by the superparamagnetic clustering effect.

${Ni_{1-x}}{Cd_x}{FeAlO_4}$의 Mossbauer 효과

고정대,홍성락,Ko, Jeong-Dae,Hong, Sung-Rak 한국재료학회 2001 한국재료학회지 Vol.11 No.10

The crystal structure and magnetic properties of the $Ni_{1-x} Cd_xFeAlO_4$(0$\leq$x$\leq$0.5) have been investigated by means of X-ray diffractometry and Mossbauer spectroscopy. The samples($0\leq$x$\leq$0.5) have been prepared by the ceramic sintering method. The X-ray diffraction pattern shows that the crystal structure of the samples is a cubic spinel type. The lattice constant has been found by extrapolation using the Nelson- Riley function and it increases slightly from $8.321{\AA}$ to $8.410{\AA}$ with Cd concentration. The Mossbauer spectra for x<0.4 show a superposition of two sextets and a paramagnetic doublet at room temperature. The cation distribution for x=0 was determined to be $[Fe_{0.75}Al_{0.25}]^A[NiFe_{0.25}Al_{0.75}^BO_4$. The superparamagnetic doublet for x< 0.4 seems to be due to A1 ion in tetrahedral site by the superparamagnetic clustering effect.

SOD 구조 형성에 따른 다이아몬드 박막 형성

고정대,이유성,강민성,이광만,이개명,김덕수,최치규,Ko, Jeong-Dae,Lee, You-Seong,Kang, Min-Sung,Lee, Kwang-Man,Lee, Kae-Myoung,Kim, Duk-Soo,Choi, Chi-Kyu 한국재료학회 1998 한국재료학회지 Vol.8 No.11

High quality diamond films of the silicon on diamond (SOD) structure are deposited using CO and $H_2$ gas mixture in microwave plasma chemical vapor deposition (CVD), a SOD structure is fabricated using low pressure CVD polysilicon on diamond/ Si(100) substrate. The crystalline structure of the diamond films which composed of { 111} and {100} planes. were changed from octahedral one to cubo-octahedron one as the CO/$H_2$ ratios are increased. The high quality diamond films without amorphous carbon and non-diamond elements were deposited at the CO/$H_2$ flow rate of 0.18. and the main phase of the diamond films shows (111) plane. The diamond/Si(lOO) structure shows that the interface is flat without voids. The measured dielectric constant. leakage current and breakdown field were $5.31\times10^{-9}A/cm^2$ and $9\times{10^7}{\Omega}cm$ respectively. CO와 $H_2$의 탄소원을 사용한 마이크로파 플라즈마 화학기상증착 방법으로 SOD 구조에 적용될 양질의 다이아몬드 박막을 형성하였고, SOD 구조를 형성하기 위해 diamond/Si(100) 구조 위에 poly-Si 박막을 저압화학기상 증착법으로 제작하였다. CO/$H_2$탄소원의 유량비 증가에 따라 다이아몬드의 결정은 octahedron 구조에서 cubo-octahedron 구조로 바뀌었으며, 결정면은 {111}과 {100}으로 혼합되어 형성되었다. 비정질 carbon과 non-diamond성분이 없는 양질의 다이아몬드 박막은 CO/$H_2$의 유량비가 0.18일 때 형성되었으며, 주 결정상은 (111) 면이었다. diamond/Si(100) 계면은 void가 없는 평활한 계면을 이루었으며, 다이아몬드 박막의 유전상수, 누설전류와 비저항은 각각 $5.31\times10^{-9}A/cm^2$ 그리고 $9\times{10^7}{\Omega}cm$이었다.

뫼스바우어 분광법에 의한 제주도 전기 분석구 스코리아의 특성 연구

고정대(Jeong Dae Ko),윤인섭(In Seop Yoon) 한국자기학회 2017 韓國磁氣學會誌 Vol.27 No.6

Fe compounds of scoria samples distributed at older cinder cone in Jeju Island were investigated by means of X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF) and Mössbauer spectroscopy. We found that samples were typical basic rock which consisted of ferromagnetic hematite, magnetite and paramagnetic augite, anorthite, albite etc. Their total amount of iron compounds including hematite, magnetite and nanophase ferric oxide, pyroxene vary 13.5 wt%~15.7 wt% by resonance absorption area. The Mössbauer spectra of the scoria samples were consisted of two sextets and two doublets. The balance state of Fe ions of all samples were chiefly Fe<SUP>3+</SUP>, and Fe<SUP>3+</SUP>/Fe<SUB>tot</SUB>. ratios were 66.55 %~91.06%.

Ni₁-xCdxFeAlO₄계의 Mossbauer 스펙트럼 연구

고정대(Jeong-Dae Ko),홍성락(Sung-Rak Hong),백승도(Seung-Do Baek) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.4

The Mossbauer spectra of the Ni_(1-x)Cd_xFeAlO₄ system were investigated with the Cd content x at room temperature. The spectra of the samples exhibit various patterns as follows 1) superparmagnetic relaxation for 0≤x≤0.2, 2) ferrimagnetic sextet for 0.3≤x≤0.5, 3) ferromagnetic relaxation for x=0.6, 0.7, 4) paramagnetic doublet for 0.8≤x≤1, with the Cd content x. In the samples with x values from 0 to 0.2, the substituted Cd²+ ions transfer the Al³+ ions from A-site to B-site mainly. The superparamagnetic relaxation effect and the ferromagnetic relaxation effect are derived from the Al³+, Cd²+ respectively. The magnetic structure of the Ni_(1-x)Cd_xFeAlO₄ system was explained by the Yafet-Kittel model.

57Fe 도프된 GaAs의 Mossbauer 효과 및 광학적 특성에 관한 연구

고정대(Jeong-Dae Ko),홍성락(Sung-Rak Hong),김득영(Deuk-Young Kim),강태원(Tae-Won Kang) 한국진공학회(ASCT) 1997 Applied Science and Convergence Technology Vol.6 No.4

GaAs내의 철(Fe)의 상태에 관한 연구를 위하여, 액상에피탁시 방법으로 Fe를 도프한 GaAs를 성장하고 성장된 에피층의 특성을 연구하였다. 도판트 물질인 Fe는 동위원소 (57)^Fe를 사용하였고, Fe이온의 GaAs내에서의 전하상태를 Mossbauer 분광실험으로 분석하였다. Mossbauer 스펙트럼으로 부터 isomer shift 값을 계산한 결과 Fe 이온은 GaAs내에서 +3가 이온 상태로 존재함을 알 수 있었다. X-ray 분석 및 photoluminescence(PL) 분광실험으로 부터 결정성이 우수한 에피층이 성장되었음을 알 수 있었으며, Fe가 도프된 GaAs의 저온 PL에서 0.99 eV 및 1.15 eV에서 피크를 갖는 반치폭이 매우 큰 발광대를 관찰 할 수 있었다. 이들 피크는 GaAs내 Fe 억셉터와 관련된 2개의 복사성 깊은 준위를 반영하는 발광현상으로 해석된다. We have investigated Mossbauer effect and emission properties of the Fe-doped GaAs grown by liquid phase epitaxy (LPE). The powder type of isotope (57)^Fe was used as a dopant source in LPE-GaAs. From the analysis of Mossbauer effect the value of isomer shift, 0.303±0.018 ㎜/sec, is calculated at low temperature. This means that charge state of Fe ion in GaAs is 3+. The results of double crystal x-ray rocking curve (DCRC) and low temperature photoluminescence (PL) show the crystal quality of the epitaxial layers are good. Unusual luminescence peaks from the Fe-GaAs epitaxial layers appeared at emission energy of 0.99 eV and 1.15 eV. We attribute these emissions to Fe-acceptor related two deep radiative centers.

제주도 한라산 남부 지역 분석구 스코리아의 철 화합물에 관한 연구

고정대(Jeong Dae Ko),최원준(Won Jun Choi) 한국자기학회 2016 韓國磁氣學會誌 Vol.26 No.6

This study reviewed mineral composition on Scoria samples of this area, atomic value state of oxidized steel, and magnetic property in order to look into characteristics of scoria that was distributed in southern area of mountainous areas, Halla Mt. of Jeju Island. By XRD analysis, mineral composition was confirmed, and characteristics of iron compounds existed in samples were investigated through Mössbauer spectroscope. Composing minerals could be learnt as feldspar basalt from XRD analysis because composting minerals were composed of quartz and feldspar anorite mainly, and iron compounds were made up with olivine, pyroxene, ilmenite, hematite, and magnetite. By Mössbauer spectroscope analysis on these iron compounds. it consisted of hematite and magnetite which showed hyperfine magnetic field of sextet mostly, and also doublet by olivine, pyroxene, ilmenite could be seen as appearing together. As a result of comparing with samples of Jeju western area having been announced in previous research, I.S. and Q.S. values of olivine, Fe2+, were 122 mm/s and 3.09~3.13 mm/s respectively, and a fact could be known that Fe<SUP>2+</SUP> olivine having similar structure each other was contained, and the ratio of Fe<SUP>3+</SUP>/Fe<SUB>tot.</SUB> was 85.90~92.82%. From these findings, it was able to be presumed that they belonged to samples having been formed on the land at the same period of time. As a result of investigating area ratio of tetrahedron (A site) and octahedron (B site) regarding magnetite in samples, it was turn out to be 0.22~0.55 less than 2.

제주도 북동부 지역 스코리아 내의 철 화합물에 대한 자기적 성질

고정대(Jeong Dae Ko),최원준(Won Jun Choi) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.1

Fe compounds of scoria samples distributed in Songdang-ri positioning north-eastern area of Jeju island were investigated by means of X-ray diffractometry (XRD) and ??Fe Mossbauer spectroscopy. The samples were prepared from six parasite. We found that the samples were composed of a typical olivine, pyroxene, ilmenite, SiO₂, anorite and anorthoclase, Mossbauer spectrum of the most scoria samples are shown doublets and sextets of olivine, doublets of pyroxene, ilmenite and silicate minerals. And the valence states of Fe ion of the scoria samples in this area are chiefly 3+ charge state and a little 2+ charge state.

제주도 한라산 후기 분석구 스코리아에 관한 Mössbauer 분광학적 연구

고정대(Jeong Dae Ko),윤인섭(In Seop Yoon) 한국자기학회 2018 韓國磁氣學會誌 Vol.28 No.6

The scoria samples is analyzed six regions formed in the several parasitic volcano in Halla Mt. on the Jeju Island. These samples is investigated for iron oxide, mineral compositions and magnetic properties by the XRD, XRF and Mössbauer spectroscopy. The results are SiO₂ is 42.74~48.69 wt%, Na₂O+K₂O is 4.41~5.76 wt%. These tapes are the tephrite basanlte, trachybasalt and basalt. The main minerals are quartz, anorthoclase, albite and diopside. Also, we can see the iron compounds such as olivine, ilmenite, hematite, magnetite. According to Mössbauer spectroscopy on these iron compounds and most are composed of hematite and magnetite, which showing the hyperfine field. Fe<SUP>3+</SUP>/Fe<SUB>tot</SUB>. ratio was analyzed as 59.70~75.60%, which is analyzed around Mt. Halla cinder cones higher than the value of the other site. Therefore, this sample were able to estimate that the formation at different points in time. The area ratio between the two sixtets is smaller than 2, which is the result of overlapping maghemite, hematite, and magnetite spectra that are not clearly distinguished at room temperature.

${Ni_{1+x}}{Ti_x}{Fe_{2-2x}}O_4$계의 $\M"{o}ssbauer$ 스펙트럼 연구

백승도,고정대,홍성락,Baek, Seung-Do,Ko, Jeong-Dae,Hong, Sung-Rak 한국재료학회 2001 한국재료학회지 Vol.11 No.1

$Ni_{1+x}/Ti_{x}Fe_{2-2x}O_4$계 시료중 스피넬의 단일상만 존재하는 x값이 0~0.7인 시료에 대한 Mossbauer 스펙트럼을 측정 분석하였다. $0{\leqq}x{\leqq}0.3$인 시료에서는 두 site의 $Fe^{3+}$ 이온에 의한 두 개의 6선 흡수선이 나타났고, $0.4{\leqq}x{\leqq}0.6$인 시료에서는 두개의 6선 흡수선과 2선 흡수선이 공존하였으며, x=0.7인 시료는 2선 흡수선만 나타났다. x값의 증가에 따라 6선 흡수선의 A-site 공명 흡수 면적이 B-site에 비해 상대적으로 커지고, 2선 홀수선의 공명 흡수면적도 6선 흡수선에 비해 커지는 것을 알 수 있었다. Mossbauer parameter중 이성질체 이동치 (I.S.)는 A-site의 경우에는 x값의 증가에 따라 커지는 반면 B-site는 큰 영향을 주지 않았고, 사중극자 분열치 (Q.S.)의 변화는 볼 수 없었으며, 두 Site의 미세자기장 ($H_{hf}$)은 X값의 증가에 따라 모두 감소하였다. 이러한 실험 결과로부터 시료의 금속 양이온 분포식을 구하였고, X값의 증가는 A-Site의 $Fe^{3+}-O^{2-}$ 결합의 공유 결합성을 약화시키는 반면 B-Site의 $Fe^{3+}O^{2-}$ 결합에는 큰 영향을 주지 않으며, 또한 X값의 증가에 따라 $Fe^{3+}\;_A-O^{2-}\;-Fe^{3+}\;_B$ 결합의 수가 감소하여 A-B 초교환 상호 작용이 약화되는 것을 알 수 있었다. $M\"{o}ssbauer$ spectra of the $Ni_{1+x}Ti_xFe_{2-2x}O_4$ systems ($0{\leqq}x{\leqq}0.7$), which appear as single phase spinel structure, were examined at RT. The $M\"{o}ssbauer$ spectra reveal two sextet for $0{\leqq}x{\leqq}0.3$, two sextet and a doublet for $0.4{\leqq}x{\leqq}0.6$, and a doublet for x=0.7 As x increases, the area ratio of B-site and A-site($A_B/A_A$) of the sextet decreases, and the area ratio of the doublet and the total areas($A_{doublet}/A_{tot.}$) increases. The isomer shift(I.S.) of A-site slightly increases and magnetic hyperfine fields($H_{hf}$) of two sites decrease as the increasing x. From these results, we have obtained the cation distributions of the samples and concluded that the increasing x leads to the decrease of covalency of $Fe^{3+}-O^{2-}$ bond in A-sites and A-B superexchange interactions.eractions.