자성 반도체 CoxFe_1-x Cr_2S_4의 전기적 특성에 관한 연구

서정철 圓光大學校 基礎自然科學硏究所 1988 基礎科學硏究誌 Vol.7 No.3

CoxFe_(1-x) Cr_2S_4 (0?X?1)시료를 진공중에 직접 합성법으로 제조하여 X선 회절법 Mossbauer 분광법, 자화율 측정법과 전기 전도도 측정법을 사용하여 연구하였다. 결정구조는 입방 spinel 구조이고 격자상수 a_0는 9.985Å∼9.927Å의 값을 갖고 있다. Mo ssbauer spectra와 자기 모우먼트 값을 액체 질소 온도에서부터 고온까지 여러온도에서 측정한 결과, 철 이온은 +2가 로서 사면체 자리에만 들어가고 초미세 자기장과 자기 모우먼트 값이 온도 상승과 더불어 같은 비율로 감소하는 사실을 발견 했으며, 자기적 정렬의 본질은 준 강자성체 임을 알았다. 온도에 따른 비 저항의 변화를 측정하여 반도체임을 확인하고 활성화 에너지는 큐리온도 이상과 이하에서 각각 0.039 eV ∼ 0.079eV, 0.014eV ∼ 0.052eV로 측정되었다. The mixed spinel system Cox Fe_(1-x) Cr_2S_4 (0〈 X〈 1) has been studied using X_rays, Mssbauer, magnetic and resistivity measurements. The crystal structure is cubic spinel and the lattice constant a_0 is found to be 9.985Å∼ 9.927Å. Mossbauer spectra, magnetic moments and resistivities have been collected from 82 K to high temperature. Fe ions are ferrous in character and occupy only tetrahedral sites. The magnetic hyperfine fields and magnetic moments decreasing with increasing temperature and it is found that the magnetic-ordering is characteristic of ferrimagnetic material. Temperature dependence of the resistivity indicates that the sampls are semiconductors and activation energies are determined to be 0.039 eV∼0.079 eV, 0.014 eV∼0.052 eV, respectively, in the higher-and lower-than-magne-tic-ordering-temperature regions.

자성 반도체 Cox Fel - x Cr₂S₄의 전기적 특성에 관한 연구

서정철 圓光大學校 1987 論文集 Vol.21 No.2

CoxFe?? Cr?S? ( 0≤X≤1)시료를 진공중에 직접 합성법으로 제조하여 X선 회절법 Mossbauer 분광법, 자화율 측정법과 전기 전도도 측정법을 사용하여 연구하였다. 결정구조는 입방 spinel 구조이고 격자상수 a?는 9.985Å ∼9.927Å 의 값을 갖고 있다. Mossbauer spectra 와 자기 모우먼트 값을 액체 질소 온도에서 부터 고온까지 여러 온도에서 측정한 결과, 철 이온은 +2가 로서 사면체 자리에만 들어가고 초미세 자기장과 자기 모우먼트 값이 온도 상승과 더불어 같은 비율로 감소하는 사실을 발견 했으며, 자기적 정렬의 본질은 준 강자성체 임을 알았다. 온도에 따른 비 저항의 변화를 측정하여 반도체임을 확인하고 활성화 에너지는 큐리온도 이상과 이하에서 각각 0.039 eV∼0.079eV, 0.014eV∼0.052eV로 측정되었다. The mixed spinel system Cox ?? ?? ( 0 <X <1 ) has been studied using X-rays, Mossbauer, magnetic and resistivity measurements. The crystal structure is cubic spinel and the lattice constant ?? is found to be 9.985 Å ∼9.927Å. Mossbauer spectra, magnetic moments and resistivities have been collected from 82K to high temperature. Fe ions are ferrous in character and occupy only tetrahedral sites. The magnetic hyperfine fields and magnetic moments decreasing with increasing temperature and it is found that the magnetic-ordering is characteristic of ferrimagnetic material. Temperature dependence of the resistivity indicates that the samples are semiconductors and activation energies are determined to be 0.039 eV∼0.079eV, 0.014eV∼0.052eV, respectively, in the higher-and lower-than-magnetic-ordering-temperature regions.

결정질 강자성체 Fe_40Ni_38의 Mo¨ssbauer 分光學的 硏究

徐廷鐵,金允坤 圓光大學校 基礎自然科學硏究所 1984 基礎科學硏究誌 Vol.3 No.1

The Crystalline Fe_40Ni_38 has been studied by Mossbauer spectroscopy from 80 to 770K. At 80K, the Mo¨ssbauer spectrum exhibits a hyperfine-field of 341 KOe. The hyperifine field H_hf(T) shows a temperature dependence of 〔H_hf(T)-H_hf(0)〕/H_hf(0)=-0.143(T/T_c)^(3/2)-0.552(T/T_c)^(5/2) for T/T_c<0.7, indicative of spin-wave excitation. The quadrupole splitting is almost zero. And the Curie temperature is determined to be T_c=770K.

Fe 합금의 超常磁性에 관한 연구

金允坤,徐廷鐵 圓光大學校 基礎自然科學硏究所 1984 基礎科學硏究誌 Vol.3 No.1

The superparamagnetic properties of the crystalline alloy Fe_40Ni_38 has been studied by Mo¨ssbauer Spectroscopy and X-ray diffractometer. Mo¨ssbauer spectra of this sample were taken at various temperatures ranging from room temperature to 778˚K. The crystal structrure and particle size were determined by X-ray diffractometer. Mo¨ssbauer spectra shows a relation between temp. and relaxation time.

Microscopic Sturdies of Crystallography in Sulphospinel Fe_(1+x)Cr_(2-x)S_4

Sur, Jung Chul,Kim, Kyung Ha 圓光大學校 基礎自然科學硏究所 1989 基礎科學硏究誌 Vol.8 No.1

Fe_(1+x)Cr_(2-x)S_4의 결정구조를 X-선 분석기와 Mo¨ssbauer 분광기를 사용하여 미시적으로 연구하였다.결정구조는 모두 입방 spinel 구조이고 결정상수 a_0는 x에 따라 9.996-9.983Å의 값을 가지고 있는 것으로 나타났다. Fe 이온은 +2가인 경우 모두 사면체 자리에 존재하며 +3가인 경우는 팔면체 자리에만 존재하는 것으로 밝혀졌다. 또한 저온에서는 비대칭적인 Mo¨ssbauer 선폭의 증가가 일어나는 것으로 보아 Jhan-Teller distortion이 존재함을 알 수 있다.

Magnetic properties of YFe<SUB>0.7</SUB>Mn<SUB>0.3</SUB>O₃ investigated with Mossbauer spectroscopy

Jung Tae LIM,Jung Chul SUR,Chul Sung KIM 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

철, 구리 스피넬 CuFe₂O₄의 Jahn - Teller 효과에 관한 연구

서정철(Jung Chul Sur),이민용(Min Yong Lee) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.2

CuFe₂O₄ was accomplished by chemical method and the crystallographic and magnetic properties have been studied by Mobauer spectroscopy and X-ray diffraction. The slowly cooled sample is found to have a tetragonal spinel structure with the lattice constant α=8.26±0.05Å, c=8.75±0.05Å. The Mobauer spectra between the room temperature to the Curie temperature show that the Cu²+ ions at octahedral site have the Jahn-Teller effect and the sample exhibits a structural phase transition near 630 K due to the Jahn-Teller effect. The Curie temperature is found to be 690K and it is lower than that of ceramic method.

M형 Ba-Ferrite에서 Fe 이온의 열 진동에 관한 연구

서정철(Jung Chul Sur),김진수(Jin Soo Ghim),최정완(Choi Jong Wan) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.1

Mossbauer and Raman spectrum studies have been carried out on the 2b-site Fe ion in the Ba-ferrite (M-type). The thermal dynamics of Fe ion was analyzed by Mossbauer spectra at different angles between the γ-ray direction and c-axis. The vibration on the 2b-site was more active compare to other direction and had very strong intensity in the Raman spectrum.

유화 Spinel Co0.95Fe0.05Cr₂S₄에서 Jahn - Teller Distortion에 의한 Mossbauer 공명 흡수선의 변화에 관한 연구

서정철(Jung Chul Sur),이민용(Min Yong Lee),고영복(Young Bok Ko) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.5

Sulphur Spinel Co_(0.95)Fe_(0.05)Cr₂S₄ has been studied with Mossbauer Spectroscopy between 4.2 K and room temperature. The Fe²+ ion in a tetrahedral site is the Jahn-Teller active and the dynamic Jahn-Teller distorts below the magnetic ordering temperature. The distortion cause a quadrupole shift to appear which increases with decreasing temperature. The magnetic hyperfine field has a maximum at 100 K and then decreases with decreasing temperature. The magnitude of the interaction ratio R between the electric quadrupole and magnetic dipole interaction increases from 0 near the magnetic ordering temperature to 5.4 at 4.2 K. The optimum values of θ, the polar angle of the magnetic hyperfine field with respect to the principle axis of the electric field gradient (EFG) remains zero and the asymmetry of the EFG η is about 0.25. The simulations of Mossbauer spectra coincidence with the experimental results.

Magnetic Properties of YFe_0.7Mn_0.3O₃ Investigated with Mössbauer Spectroscopy

Lim, Jung Tae,Kim, Sam Jin,Sur, Jung Chul,Kim, Chul Sung American Scientific Publishers 2018 Science Of Advanced Materials Vol.10 No.5

<P>The polycrystalline YFe0.7Mn0.3O3 sample was synthesized by using standard solid state reaction method. The crystalline structure and magnetic properties of sample were investigated with X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), and Mossbauer spectroscopy. From the refined XRD patterns at 295 K, YFe0.7Mn0.3O3 sample was found to be single-phased with the Bragg factor (R-B) and structure factor (R-F) of 3.88 and 3.67%, respectively. The YFe0.7Mn0.3O3 sample was determined to be orthorhombic with space group Pnma, and lattice constant a(0), b(0) and c(0) of sample were 5.647, 7.544 and 5.273 angstrom, respectively. Based on the field-dependent magnetization curves of YFe0.7Mn0.3O3 sample up to 10 kOe at 295 K, the sample shows weak ferromagnetic behavior because of Fe-O-Fe and Fe-O-Mn. From the temperature dependence of magnetization curves under 100 Oe between 4.2 and 300 K, YFe0.7Mn0.3O3 sample show spin reorientation from antiferromagnetic to weak ferromagnetic around 265 K. We have obtained Mossbauer spectra of YFe0.7Mn0.3O3 sample at various temperature ranging from 4.2 to 295 K. Mossbauer spectra were least-square fitted as a function of the Fe atom distribution below Curie temperature (T-c). From the analyzed Mossbauer spectra, YFe0.7Mn0.3O3 sample have shown abrupt changes in the magnitude and slope of hyperfine field (H-hf) and electric quadrupole shift (E-Q) around spin reorientation temperature. In addition, the obtained value of isomer shift (delta) show that the charge state of Fe ions is Fe3+ high spin.</P>