Spin-Peierls 전이를 하는 CuGeO₃계의 이온 치환 효과

이영배,채광표,권우현,백서욱,이성호 건국대학교 자연과학연구소 1998 建國自然科學硏究誌 Vol.9 No.1

Spin-Peierls 전이를 하는 CuGeO₃계에 원소를 치환했을 때의 자기적 및 결정학적 특성을 비교 검토하고, 직접 Cu₁-xGe₁-xFe₂O₃(x=0.05, 0.1) 시료를 제조하여 SQUID, Mssbauer 분광기, X-선 회절 방법으로 연구하였다. 이 시료의 결정구조는 orthorhombic 이고 격자 상수는 x= 0.05 때 a = 4.795Å, b=8.472Å, c=2.904Å 이고 x=0.1때는 a=4.784Å, b=8.472Å, c=2.904Å였다. 상온에서 Mssbauer 스펙트럼은 Fe³+ 이온의 사면체 자리에 의한 이중선과 팔면체 자리에 의한 Zeeman 선으로 중첩되어 나타났고 자기감수율의 극대점과 Mssbauer 변수의 불연속으로부터 본 시료의 spin-Peierls 전이 온도는 13K 임을 알아냈다. The magnetic and crystallograpic properties of the substituted spin-Peierls transition CuGeO₃ system have been reviewed, and we synthesized the Cu₁-xGe₁-xFe₂xO₃ (x=0.05 and x=0.1) system and studied by superconducting quantum interference device, Mossbauer spectrometer and x-ray diffractometer. The crystal structure is orthorhombic and the lattice constants are decreased as increasing iron contents. That is, in Cu₁-xGe₁-xFe₂xO₃ system a=4.795Å, b=8.472Å and c=2.932Å for x=0.05, and a=4.784Å, b=8.472Å and c=2.904Å for x=0.1 respectively. The Mossbauer spectra are superposition of the doublet due to the Fe³+ ions at tetrahedral sites and the sextet due to the Fe³+ ions at octahedral sites at room temperature. From the cusp of the magnetic susceptibility and the discontinuity of Mossbauer parameters we found the spin-Peierls transition temperature of our samples is 13K.

Y-Gd-In-Fe-O계의 분자장 상수와 교환상수의 결정

이영배,채광표 建國大學校 自然科學硏究所 1997 建國自然科學硏究誌 Vol.8 No.-

The substituted Yttrium Iron Garnet(YIG) systems Y-Gd-In-Fe-O have been investigated by means of X-ray diffractometry and SQUID. The specimens have been found to be the cubic garnet structure in the entire compositions. From the magnetization curve measured by means of SQUID and Dionne's formula related to cation distribution, molecular field-and exchange constants were determinated.

Mossbauer 분광법에 의한 Fe₂SiO₄의 연구

이성호,김웅태,채광표,정덕조 建國大學校基礎科學硏究所 1988 理學論集 Vol.13 No.-

Fe₂SiO₄에 관한 X-선 회절실험과 Mossbauer 분광실험을 하였다. X-선 회절실험 결과 본 시료는 olivine group에 속하는 fayalite로서 orthorhombic 구조(??)임을 알 수 있었다. Mossbauer 분광실험은 60K-834K의 온도구간에서 행하여 졌으며, Mossbaure 스펙트럼을 분석한 결과 철은 high spin 2+ 상태임을 알 수 있었고, X-선 회절실험 결과와는 다르게 철이 산소 이온들과 함께 일그러진 octahedron을 형성하고 있음을 알 수 있었다. The Fe₂SiO₄ has been studied by means of X-ray diffractometry and Mossbauer spectroscopy. The analysis of X-ray diffraction pattern shows that Fe₂SiO₄is fayalite of orthorhombic structure(??). The Mossbauer spectra which have been taken between 60K and 834K show that the valence state of iron is ferrous and high spin state and that the iron ions occupy sites of distorted octahedron whereas the X-ray analysis shows it is at a site of regular one.

Effects of Ga Substitution on Crystallographic and Magnetic Properties of Co Ferrites

Kwang Pyo Chae,Won-Ok Choi,Byung-Sub Kang,Young Bae Lee 한국자기학회 2015 Journal of Magnetics Vol.20 No.1

The crystallographic and magnetic properties of gallium-substituted cobalt ferrite (CoGaxFe2-xO₄) were investigated. The new material was synthesized using conventional ceramic methods, with gallium substituted for ferrite in the range of x = 0.0 to 1.0, in steps of 0.2. X-ray diffraction and Mossbauer spectroscopy were used to confirm the presence of crystallized particles in the CoGaxFe2-xO₄ ferrite powders. All of the samples exhibited a single phase with a spinel structure, and the lattice parameters decreased as the gallium content increased. The particle size of the samples also decreased as gallium increased. For x ≤ 0.4, the Mossbauer spectra of CoGaxFe2-xO₄ could be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of Fe<SUP>3+</SUP> with A- and B-sites. However, for x ≥ 0.6, the Mossbauer spectra could be fitted with two Zeeman sextets and one doublet. The variation in the Mossbauer parameters and the absorption area ratio indicated a cation distribution of (Co0.2-0.2xGaxFe0.8-0.6x)[Co0.8+0.2xFe1.2-0.4x]O₄, and the magnetic behavior of the samples suggested that the increase in gallium content led to a decrease in the saturation magnetization and in the coercivity.

Crystallographic and Magnetic Properties of Li<SUB>0.7</SUB>Co<SUB>0.2</SUB>Ti<SUB>0.2</SUB>V<SUB>0.2</SUB>Fe<SUB>1.7</SUB>O₄ Ferrite

Kwang Pyo Chae,Woo Hyun Kwon,Jae-Gwang Lee 한국자기학회 2010 Journal of Magnetics Vol.15 No.1

This study examined the crystallographic and magnetic properties of vanadium-substituted lithium cobalt titanium ferrite, Li0.7Co0.2Ti0.2V0.2Fe1.7O₄. Ferrite was synthesized using a conventional ceramic method. The samples annealed below 1040 ℃ showed X-ray diffraction peaks for spinel and other phases. However, the sample annealed above 1040 ℃ showed a single spinel phase. The lattice constant of the sample was 8.351 A, which was relatively unaffected by vanadium-substitution. The average grain size after vanadium- substitution was 13.90 ㎛, as determined by scanning electron microscopy. The Mossbauer spectrum could be fitted to two Zeeman sextets, which is the typical spinel ferrite spectra of Fe<SUP>3+</SUP> with A and B sites, and one doublet. From the absorption area ratio of the Mossbauer spectrum, the cation distribution was found to be (Co0.2V0.2Fe0.6)[Li0.7Ti0.2Fe1.1]O₄. Vibrating sample magnetometry revealed a saturation magnetization and coercivity of 36.9 emu/g and 88.6 Oe, respectively, which were decreased by vanadium-substitution.

Synthesis and Magnetic Properties of Electrodeposited Cobalt-Iron-Vanadium Thin Films

Chae, Kwang-Pyo The Korean Magnetics Society 2006 Journal of Magnetics Vol.11 No.2

CoFeV thin film alloys were fabricated by electrodeposition, and the dependences of their magnetic properties on the current density were investigated using an X-ray diffractometer and a vibrating sample magnetometer. The deposited Co increased from about 45 to 60 wt.% with increasing current density until $25mA/cm^2$ whereas the deposited Fe decreased from about 55 to 40 wt.% with increasing current density until $25mA/cm^2$. The deposited V, about 2 wt.%, was independent of the current density. The current efficiencies of electrodeposition decreased linearly from about 40 to 29% with increasing current density. The X-ray diffraction measurement showed that all peaks of the CoFeV films were consistent with those of a typical Co hcp and Fe bcc mixed phase. An increase in the current density decreased the grain size and increased the lattice constant. The saturation magnetization increased from about 2.2 to 2.5 T with increasing current density. The coercivity measured in the perpendicular direction decreased from 260 to 120 Oe with increasing current density; a drastic drop of 60 Oe occurred at $5mA/cm^2$. The coercivity measured in the in-plane direction remained almost unchanged, at about 20 Oe, with increasing current density.

Comparison of the Substituted YIG with In and Fe by Mo¨ssbauer Spectroscopy

Chae, Kwang-Pyo 건국대학교 1994 學術誌 Vol.38 No.2

YIG에서 Y이온을 In과 Fe로 치환시킨 물질을 제조하여 결정학적 특성과 자기적 특성을 Mo¨ssbauer분광법과 X-선 회절방법으로 비교 분석하였다. 이 계의 구조는 YIG와 같은 구조였으나, 치환량이 증가함에 따라 격자 상수는 이온 반경이 큰 In으로 치환시킨 계가 더 빨리 증가하였다. a-자리와 d-자리에 위치한 Fe3+에 의한 두 Zeeman sextet는 치환량이 증가함에 따라 네 개로 갈라짐을 알아냈다. 또 치환량이 증가함에 따라 In 으로 치환시킨 계의 초미세 자기장(MHF)은 서서히 감소하였으나 Fe로 치환시킨 계는 a-와 d-자리의 MHF가 모두 증가했다. 이러한 현상을 구조적인 일그러짐에 기인하는 초교환 상호작용과 혹은 초교환 상호작용 각도의 변화로 설명할 수 있었다. 또한 Mo¨ssbauer 스펙트럼의 흡수율을 이용하여양이온 분포식을 알아냈으며, 두 계의 Neel온도 변화를 초교환 상호작용의 세기와 연관시켜 해석하였다. The crystallographic and magnetic properties of substituted YIG systems with In and Fe have been compared by Mo¨ssbauer spectroscopy and X-lay diffractometry. The structure of these systems are YIG structure in the entire composition range, but the lattice constants some more rapidly increase with increasing x in Y3-xInxFe5O12 than that in Y3-xFe5+xO12 due to the larger radius of substituted In ions. The two Zeeman sextet from Fe3+ at a-sites and d-sites begin to split into four subsextets with increasing x. The MHF of In substituted system slowly decreased with increasing x, but that of Fe substituted system increased at a- and d-sites with increasing x. This can be interpreted as superexchange interaction due to the structural distortion and/or variation of angle for superexchange interaction. The cation distribu-tion are also estimated from absorption ratio of Mo¨ssbauer spectra, and the variation of Neel temperature discussed on these two systems related to the strength of superexchange interaction.

Debye Temperature and Force Constant of Y_(3-x)Gd_(x)Fe_(4.8)In_(0.2)O_12 System

Chae, Kwang-Pyo 건국대학교 1995 學術誌 Vol.39 No.2

Mo¨ssbauer 분광법과 x-ray 회절 방법을 이용하여 희토류 원소로 치환한 Y3-XGdXFe4.8In0.2O12 계의 결정학적 특성을 연구하였다. 특히 조성비 변화에 따른 Debye 온도와 힘상수(force constant)를 측정하였다. 전체적으로 YIG 구조를 가지는 이 계는 Gd 이온의 치환량이 증가할수록 격자 상수가 증가하였으며 Neel 온도도 증가하였다. 또 Debye 온도와 힘상수가 Gd의 치환량이 많아질수록 커지는 것으로 나타났는데 이는 양이온-음이온 사이의 결합력의 증가로 해석할 수 있다. The crystallographic properties of Y3-XGdXFe4.8In0.2O12 system have been studied by Mo¨ssbauer spectroscopy and x-ray diffraction method. Especially the Debye temperature and the force constant versus composition are measured. The structure of this system is YIG structure, and the lattice constant and Neel temperature are increased with increasing Gd contents. And the rise of the Debye temperature and the force constants with increasing Gd contents could be interpreted as the increasement the strength of cation-anion bond.

Mossbauer Study of YIG Substituted with In

Chae,Kwang-Pyo,Lee,Young-Bae 建國大學校 附設 自然科學硏究所 1993 建國自然科學硏究誌 Vol.4 No.-

준강자성체인 YIG에서 Y 이온을 In 이온으로 부분 치환시켜 만든 Y₃-xInxFe5O12 (x=0.00, 0.18, 0.33, 0.60)를 제조하여 X-ray 회절과 Mossbauer분광법으로 자기적 특성 및 구조를 연구하였다. 전체 조성비 범위에서 YIG와 같은 구조였으나 격자상수는 x 값이 증가할수록 증가하였는데 이는 치환된 이온 반경이 크기 때문이다. Mossbauer spectrum은 상온에서 Fe ³+ 이온이 a, a'와 d, d'자리에 위치하는 4개의 Zeeman을 나타냈다. Neel 온도는 x값이 증가할수록 각각 523K(x=0.18), 518K(x=0.33), 495K(x=0.60)로 나타났는데, 이로부터 In이온이 많아질수록 superexchange interaction이 감소함을 알 수 있었다. The Y₃-xInxFe5O12 system(x=0.00, 0.18, 0.33, 0.60) has been investigated by means of X-ray diffractometry and Mossbauer spectroscopy. The structure of the system is YIG structure in the entire composition range and the lattice constants increased with increasing x due to the large radii of substituted ions. Four Zeeman lines from ³+ ions at, a, a' and d, d' -sites have been observed at room temperature. The Neel temperature decreased with increasing x as 523K(x=0.18), 518K(x=0.33), and 495K(x=0.60), respectively, which indicates the superexchange interaction is weakened with increasing In ions.

The Debye Temperature of Fe₂O₃(Al₂O₃)_0.5(SiO)_0.79

Chae, Kwang-Pyo 건국대학교 1988 論文集 Vol.26 No.1

고온 합성법을 이용하여 Fe2O3(Al2O3)0.5(SiO)0.79를 제작하여, X-ray 회절과 Messbauer 분광 실험을 하였다. 위 실험 결과로 미루어, 제작된 시료는 매우 무질서한 구조를 갖는것으로 보였으며, 온도 범위 50-700K에서 Mo¨ssbauer spectrum은 비대칭 사중극자 이중선으로 나타났으며 magnetic ordering 현상은 없었다. Mo¨ssbauer 흡수선들의 면적비로부터 구한 Debye 온도는 θ=276±5K였고, Fe 이온은 Fe2+상태로 존재함을 알아냈다.