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NdFe10.7TiM0.3(M = B, Ti)의 Mossbauer 연구
김철성(Chul Sung Kim),이용종(Young Jong Lee),김윤배(Y. B. Kim),김창석(C. S. Kim) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.1
The authors have studied crystallographic and magnetic properties of NdFe_(10.7)TiM_(0.3)(M = B, Ti) by X-ray diffraction, VSM magnetometer, and Mossbauer spectrometer. The Alloys were prepared by arc-melting under argon atmosphere. The NdFe_(10.7)TiM_(0.3) has pure single phase, whereas the NdFe_(10.7)TiM_(0.3) contains some α-Fe, from powder X-ray diffractometry. The NdFe_(10.7)TiM_(0.3) has the ThMn₁₂-type tetragonal structure with α_0=8.587 A and C_0= 4.788 Å. The Curie temperature (Tc) is 570 ± 3 K from Mossbauer spectroscopy performed at various temperatures ranging from 13 to 770 K. Each spectrum of below Tc was fitted with five subspectra of Fe sites in the structure (8i₁,8i₂, 8j₁, 8j₂ and 8f). The area fraction of the subspectra at room temperature are 16.4, 8.2, 14.8, 21.3 and 39.3 %, respectively. Magenetic hyperfine fields for the Fe sites decrease in the order, Hhf(8i)>Hhf(8f)>Hhf(8f).
ThMn₁₂형 NdFe10.7Ti1.2Mo0.1의 미세구조 및 자기적 성질 연구
안성용(Sung Yong An),이승화(Seung Wha Lee),김철성(Chul Sung Kim),김윤배(Y. B. Kim),김창석(C. S. Kim) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.2
We have studied crystallographic and magnetic properties of NdFe_(10.7)Ti_(1.2)Mo_(0.1) by Mossbauer spectroscopy, X-ray diffraction and vibrating sample magnetometer(VSM). The alloys were prepared by arc-melting under an argon atmosphere. The NdFe_(10.7)Ti_(1.2)Mo_(0.1) has pure a single phase, whereas NdFe_(10.7)Ti_(1.3) contains some α-Fe, conformed with X-ray diffractometry and Mossbauer measurements. The NdFe_(10.7)Ti_(1.2)Mo_(0.1) has a ThMn₁₂-type tetragonal structure with a_0=8.637Å and c_0=4.807Å. The Curie temperature (Tc) is 600 K from the result of Mossbauer measurement performed at various temperatures ranging from 13 to 800 K. Each spectrum of below Tc is fitted with five subspectra of Fe sites in the structure (8i₁, 8i₂, 8j₂, 8j₁, 8f). The area fractions of the subspectra at room temperature are 12.3%, 14.0%, 21.0%, 11.8%, 40.9%, respectively. Magnetic hyperfine fields for the Fe sites decrease in the order, Hhf(8i)>Hhf(8j)>Hhf(8f). The abrupt changes in the magnetic hyperfine field, an magnetic moment observed at about 160 K in NdFe_(10.7)Ti_(1.2)Mo_(0.1) are attributed to spin reorientations. The average hyperfine field of the NdFe_(10.7)Ti_(1.2)Mo_(0.1) shows a temperature dependence of [Hhf(T)-Hhf(0)]/Hhf(0) = -0.34(T/Tc)((3/2)-0.14(T/Tc)^(5/2) for T/Tc<0.7, indicative of spin wave excitation. The Debye temperatures of NdFe_(10.7)Ti_(1.2)Mo_(0.1) is found to be Θ = 340±5 K.
NdFe10.7Ti1.3의 결정학적 및 자기적 성질 연구
이승화(Seung Wha Lee),이용종(Young Jong Lee),안성용(Sung Yong An),김철성(Chul Sung Kim),김윤배(Y. B. Kim),김창석(C. S. Kim) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.6
NdFe_(10.7)Ti_(1.3) has been studied with X-ray diffraction, Mossbauer spectroscopy and vibrating sample magnetometer(VSM). The alloys were prepared by arc-melting under an argon atmosphere. The NdFe_(10.7)Ti_(1.3) contains some α-Fe, from X-ray and Mossbauer measurements. The NdFe_(10.7)Ti_(1.3) has the ThMn₁₂-type tetragonal structure with α_0=8.607 Å and c_0=4.790 Å. The Curie temperature(Tc) of the NdFe_(10.7)Ti_(1.3) is 590 K from Mossbauer spectroscopy performed at various temperatures ranging from 13 to 800 K. Each spectrum below Tc was fitted with six subspectra of Fe sites in the structure(8i₁, 8i₂, 8j₂, 8j₁, 8f and α-Fe). The area fractions of the subspectra at room temperature are 13.8 %, 15.4 %, 17 %, 16.4 %, 34.1 % and 3.3 %, respectively. Magenetic hyperfine fields for the Fe sites decrease in the order, Hhf(8i)>Hhf(8j)>Hhf(8f). The abrupt changes in the magnetic hyperfine field, isomer shift and magnetic moment observed at about 180 K in NdFe_(10.7)Ti_(1.3) are attributed to spin reorientation.
Mossbauer Study of Co0.3Fe0.7Cr₂S₄
김철성(C. S. Kim),하민용(M. Y. Ha),이운화(W. H. Lee),윤성로(S. R. Yoon),서정철(J. C. Sur) 한국자기학회 1992 韓國磁氣學會誌 Vol.2 No.3
Co_(0.3)Fe_(0.7)Cr₂S₄ has been studied by Mossbauer spectroscopy and X-ray diffraction, The crystal structure is found to be a cubic spinel with the lattice parameter α。=9.967 Å. Mossbauer spectra have been collected over the temperature range 12 K ~ 300 K. The absence of quadrupole splitting above the Neel temperature T_N indicates that iron ions occupy only the tetrahedral (A) sites, The isomer shift indicates that the charge state of a Fe ion is ferrous in character. It is notable that as the temperature decreases below T_N=184 K, both quadrupole splitting and asymmetrical line broadening appear and increase with decreasing temperature, suggesting the appearence of a dynamic Jahn-Teller distortion. The magnetic hyperfine field and quadrupole splitting at 12 K are found to be 193 kOe and 1.10 ㎜/s, respectively, Debye temperature is found to be 218 K.
Fe 이온이 단사결정 NiCr₂S₄에 미치는 자기적 성질에 관한 연구
김철성(C. S. Kim),고흥문(H. M. Ko),박재윤(J. Y. Park) 한국자기학회 1992 韓國磁氣學會誌 Vol.2 No.3
Ni_xFe_(1-x)Cr₂S₄ has been studied by Mossbauer and X-ray technique and the crystal structure is found to be monoclinic in the composition range 0.9≤x≤1.0 Mossbauer spectra of Ni_xFe_(1-x)Cr₂S₄ have been taken at various temperatures ranging from 12 K to room temperature. The isomer shift indicates that the charge state of Fe ions is ferrous in character and temperature dependence of isomer shift is in good agreement with theoretical value. Magnetic ordering of antiferromagnetic nature exists below the Neel temperature, T_N=200 K and magnetic hyperfine and quadrupole interactions at 81 K have been studied, yielding the following results : Hhf=156 kOe, ΔE_Q= 2.15 ㎜/s, θ=59˚, Φ=90 0, and η=0.9 for Ni_(0.99)Fe_(0.01)Cr₂S₄. The Neel temperature T_N increases linearly, suggesting that the superexchange interaction for the Ni-S-Cr link is stronger than that for the Fe-S-Cr link.
이충섭(C. S. Lee),이찬영(C. Y. Lee),김철성(C. S. Kim),지상희(S. H. Ji) 한국자기학회 1993 韓國磁氣學會誌 Vol.3 No.1
The cationic distributions and magnetic properties of Cu_xZn_(1-x)Fe₂O₄(0 ≤ x ≤ 1) have been studied by X-ray diffraction and Mossbauer spectroscopy. The crystal structures are cubic spinels in the range 0 ≤ x ≤ 0.9. The ionic distribution of ZnFe₂Zn_(1-x)Fe_x)_A[Zn_xFe_(2-x)]_BO₄, where x=0.1. The distribution of Fe³+ ions was extracted from the Mossbauer spectra below Curie temperature in the whole range 0 ≤ x ≤ 1. The number of Fe³+ ions in the tetrahedral sites and Curie temperature of Cu-Zn ferrite increase with increasing Cu-concentration.