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Mossbauer 분광학을 이용한 Ni0.5Co0.5Fe₂O₄의 Atomic migration 연구
이승화(Seung Wha Lee),홍성렬(Sung Real Hong),박승일(Seung leI Park),김철성(Chul Sung Kim) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.1
The crystallographic and magnetic properties of the ferrimagnetic Ni_(0.5)Co_(0.5)Fe₂O₄ have been studied by X-ray and Mossbauer measurements. The Crystal structure is found to be spinel structure with the lattice constant a_0 = 8.346 ± 0.005 Å. Mossbauer spectra of Ni_(0.5)Co_(0.5)Fe₂O₄ have been taken at various temperatures rauging from 13 to 780 K. The isomer shifts indicate that the valence states of the Fe ions for tetrahedral(A) and octahedral (B) sites have ferric character. Debye temperatures for the A and B sites are found to be 441± 5 K and 321± 5 K, respectively. Atomic migration from the A to the B sites starts near 500 K and increases rapidly with increasing temperature to such a degree that 51 % of the ferric ions at the A sites have moved over to the B sites by 700 K.
Cu - Ni Ferrite의 결정학적 및 Mossbauer 연구
김우철(Woo Chul Kim),홍성렬(Sung Real Hong),지상희(Sang Hee Ji),이승화(Seung Wha Lee),엄영랑(Young Rang Uhm),김철성(Chul Sung Kim) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.2
Cu_(0.9)Ni_(0.1)Fe₂O₄ 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=8.386Å. The Curie temperture is determined to be Tc=755 K for a heating rate of 5K/min. The Mossbauer spectra consist of two six-line patterns corresponding to Fe³+ 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)Fe₂O₄ 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.
Ni0.65Zn0.35Cu0.1Fe1.9O₄의 결정학적 및 Mossbauer 효과 연구
김우철(Woo Chul Kim),이승화(Seung Wha Lee),홍성렬(Sung Real Hong),옥항남(Hang Nam Oak),김철성(Chul Sung Kim) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.3
Ni_(0.65)Zn_(0.35)Cu_(0.1)Fe_(1.9)O₄ has been studied with Mossbauer spectroscopy and X-ray diffraction. The crystal structure is found to be a cubic spinel with the lattice constant α。=8.390 Å. Mossbauer spectra of Ni_(0.65)Zn_(0.35)Cu_(0.1)Fe_(1.9)O₄ has been taken at various temperatures ranging from 12 K to 705 K. The isomer shift indicates that iron ions are ferric at tetrahedral [A] and octahedral sites [B], respectively. The Neel temperture is determined to be T_N=705 K. As the temperature increases toward T_N a systematic line broadening effect in the Mossbauer spectrum is observed and interpreted to originate from different temperature dependencies of the magnetic hyperfine fields at various iron sites. The quadrupole splitting just on T_N is 0.41 ㎜/s whereas the quadrupole shift below T_N vanishes. This implies that the orientation of the magnetic hyperfine field with respect to be principal axes of the electric field gradient is random.
이승화(Seung Wha Lee),김동회(Dong Hoi Kim),김우철(Woo Chul Kim),홍성렬(Sung Real Hong),김철성(Chul Sung Kim) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.1
The crystallographic and magnetic properties of the ferrimagnetic CoFe_(1.9)Ga_(0.1)O₄ have been studied by X-ray, Mossbauer measurements. The crystal structure is found to be inverse spinel structure with the lattice constant a_0 = 8.386±0.005 Å. Mossbauer spectra of CoFe_(1.9)Ga_(0.1)O₄ have been taken at various temperatures ranging from 13 to 840 K. The isomer shifts indicate that the valence states of the Fe ions for tetrahedral (A) and octahedral (B) sites have ferric character. Debye temperatures for the A and B sites are found to be 882±5 K and 209±5 K, respectively. Atomic migration from the A to the B sites starts near 350 K and increases rapidly with increasing temperature to such a degree that 73 % of the ferric ions at the A sites have moved over to the B sites by 700 K.
Crystallographic and Magnetic Properties of Co_x(Cu_0.5Fe_0.5)_1-xCr_2S_4
Ok, Hang Nam,Baek, Kyung Seon,Sur, Jung Chul,Kim, Yun Kon,Hong, Sung Real 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
x선 및 뫼스바우어 측정법을 사용하여 혼성 결정계열 Co(Cu_0.5Fe_0.5)_1-xCr_2S_4를 연구해본 결과. 결정구조는 입방스피넬구조를 갖고 있으며 격자상수는 Vegard의 법칙을 만족하고 있었다. 이성질체이동치로부터 철이온의 전하상태가 +3가 상태임을 알았다. 또한 전기사중극자 분열의 소멸로부터 철이온이 사면체자리를 차지하고 있음을 알았다. 특기할점은 80K에서 측정한 모든 뫼스바우어양들의 구성성분의 변화에 대해서 불변이라는 것이다. 이현상은 철이온 주변원자의 특이한 배치상태를 토대로 하여 설명할 수가 있다. Neel온도는 Co농도증가와 더불어 급속히 감소하였는데 이는 Co^2+-S-Cr^3+ 초교환 상호작용이 Fe^3+-S-Cr^3+ 초교환 상호작용에 비하여 상당히 약함을 의미한다. The mixed series Co_x(Cu_0.5)_(1-x)Cr_2S_4 has been studied using x-ray Mossbauer techniques. The crystal structure is found to be cubic spinel. and the lattice parameter a_0satisfies Vegard's law. The isomer shifts indicate that Fe ions are ferric and the absence of quadrupole splitting suggests the iron ions occupy. only tetrahedral sites. It is notable the all the Mossbauer Parameters at 80 K are independent of the com-position. This has been explained in terms of local atomic arrangements. The Neel temperature decreases rapidly with increasing cobalt concentration. suggesting that the superexchange interaction for the Co^2+-S-Cr^3+ link is much weaker than that for the Fe^3+-S-Cr^3+ link.