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57Fe를 미량 치환한 La - Ca - Mn - O의 초거대자기저항과 Mossbauer분광학 연구
박승일(Seung-Iel Park),김철성(Chul Sung Kim) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.6
Colossal magnetoresistance La_(0.67)Ca_(0.33)Mn_(0.99)(57)^Fe_(0.01)O₃ material has been produced by a metal-salt routed sol-gel process method. Magnetic properties of La_(0.67)Ca_(0.33)Mn_(0.99)(57)^Fe_(0.01)O₃ have been studied with x-ray diffraction, Rutherford back-scattering spectroscopy (RBS), vibrating sample magnetometer, and Mossbauer spectroscopy. Crystalline La_(0.67)Ca_(0.33)Mn_(0.99)(57)^Fe_(0.01)O₃ was perovskite cubic structure with a lattice parameter a_0 = 3.868 Å. And there was no appreciable change in the value of the lattice parameter when a small amount (x = 0.01) of iron was added. However, Mossbauer and VSM data indicate the Curie temperature of the La_(0.67)Ca_(0.33)Mn_(0.99)(57)^Fe_(0.01)O₃ decreased from 282 to 270 K and also the saturation magnetization from 84 to 81 emu/g at 77 K. Mossbauer spectra of La_(0.67)Ca_(0.33)Mn_(0.99)(57)^Fe_(0.01)O₃ have been taken at various temperatures ranging from 4.2 K to room temperature. Analysis of (57)^Fe Mossbauer data in terms of the local configurations of Mn atoms has permitted the influence of the magnetic hyperfine interactions to be monitored. The isomer shifts show that the charge state of all Fe ions are ferric. The magnetoresistance of La_(0.67)Ca_(0.33)Mn_(0.99)(57)^Fe_(0.01)O₃ was about 33 % at semiconductor-metal transition temperature T_(SC-M) = 250 K.
철을 미량 치환한 ZnO 희박자성반도체의 결정학적 및 자기적 특성 연구
안근영(Geun Young Ahn),박승일(Seung-Iel Park),김삼진(Sam Jin Kim),김철성(Chul Sung Kim) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.2
Zn_(1-x)(57)^Fe_xO (x=0.01, 0.02, 0.03) compounds were fabricated using the solid-state reaction method. In order to determine magnetic behavior and ionic state of the doped transition metal ((57)^Fe) in ZnO, we carried out Mossbauer measurements at various temperatures ranging from 13 to 295K. Mossbauer spectra for Zn_(0.97)(57)^Fe_(0.03)O at 4.2K have shown the ferromagnetic phase (sextet), but the only paramagnetic phase (doublet) is seen at 295K. The hysteresis loop below 77K for Zn_(0.97)(57)^Fe_(0.03)O indicated the coexistence of ferromagnetic and paramagnetic phases.