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외부자기장 뫼스바우어 분광기를 이용한 Li0.5Fe2.5-xRhxO₄의 자기적 성질과 결정학적 구조에 관한 연구
강건욱(Kun Uk Kang),김철성(Chul Sung Kim) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.6
Li_(0.5)Fe_(2.5-x)Rh_xO₄(x=0.25, 0.50, 0.75, 1.00) has been prepared by solid state reaction. Crystallographic and magnetic properties were investigated by Mossbauer spectroscopy, SQUID magnetometry, and x-ray diffraction. The crystal structure is found to be a cubic spinel structure with space group Fd3m for all the samples. The lattice constant a。 increases from 8.3365 Å to 8.3932 Å with increasing Rh concentration x. The migration of Li ion has been confirmed by x-ray patterns and the results of applied field Mossbauer analysis. The temperature dependence of the absorption area of each site was analyzed with the Debye model for the recoil-free fraction. The Debye temperature for the octahedral sites is almost as large as for the tetrahedral sites, thereby suggesting similar interatomic binding forces for the octahedral and the tetrahedral sites. The saturated magnetic moment and the Mossbauer spectra taken at 4.2 K under the applied field (6 T) show that the spin structure of Li_(0.5)Fe_(2.5-x)Rh_xO₄ is compatible with the collinear Neel Model.
조준희,고상길,안양규,강건욱,안동현,최은정,Cho, Jun-Hee,Ko, Sang-Gil,Ahn, Yang-Kyu,Kang, Kun-Uk,An, Dong-Hyun,Choi, Eun-Jung 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.2
계면활성제를 첨가한 음향화학적 침전법으로 두 가지 크기의 아연페라이트 나노입자를 합성하였다. 열분석장치(TGA/DSC)를 이용하여 열적 특성 및 결정화 온도를 조사하였고, 결정구조 확인을 위하여 X선 회절실험을 실시하였다. 제조된 입자는 $240^{\circ}C$ 부근에서 결정생성이 시작되었으며, 결정구조는 전형적인 스피넬 구조를 나타내었다. Scherrer식에 의해 측정된 입자의 크기는 11.2nm와 13.4nm이었다. SQUID를 통하여 자기적 성질을 분석한 결과, 작은 크기의 입자에 대한 방해온도 $T_B$(Blocking temperature)가 큰 입자의 경우보다 더 높게 나타났다. Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized zinc ferrite particles using chemical co-precipitation technique through a sonochemical method with surfactant such as oleic acid. The thermal behaviour of the zinc ferrite was determined by the thermoanalytical techniques (TGA-DSC). Powder X-ray diffraction measurements show that the samples have the spinel structure. Magnetic properties measurement were performed using a superconducting quantum interference device (SQUID) magnetometer.