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Study on the Magnetic Behavior of In-doped Nickel Chromite by Using Mössbauer Spectroscopy
현성욱,김철성,Seung-Iel Park,오영제 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2
NiCr_(1.9−x)^(57)Fe_(0.1)In_xO_4 (x = 0.0, 0.1, 0.3, and 0.5) was prepared by using a sol-gel method. The crystal structure at room temperature was determined to be a normal cubic spinel with space group Fd3m. An analysis of the x-ray diffraction patterns was performed using a Rietveld refinement method while the Bragg R_B and R_F factors were below 5%. The magnetic Néel temperature decreased from 150 K to 77 K with increasing In concentration, which was confirmed by zero-fieldcooled (ZFC) magnetization at applied fields under 100 Oe and by Mössbauer spectra measured at various temperatures. Magnetic hysteresis loops of the samples at 77 K showed drastically increasing magnetization and decreasing coercivity with increasing In concentration. The Mössbauer spectra of the samples were measured at various temperatures ranging from 4.2 to 295 K. The isomer shift value showed that the charge states of the iron ions are ferric. The Mössbauer spectra showed two magnetic phases with two different magnetic spin direction sites for the Cr^(3+) ion state. Mössbauer spectra below 77 K showed 6 sharp absorption lines and the linewidth became broader with increasing temperature, which indicates a Jahn-Teller distortion and relaxation.
頭部放射線計側寫眞에 依한 脣, 口蓋裂者의 顎顔面 成長에 關한 硏究
徐廷勳,玄成旭 대한치과교정학회 1982 대한치과교정학회지 Vol.12 No.2
A cephalometric radiographic cross sectional comparative study was undertaken to investigate craniofacial growth in cleft lip and palate individuals. The material for this study consisted of 43 subjects with operated cleft lip and palate. (29 males, 14 females). The range of age was from 6 years to 12 years. The roentgenocephalometric values of cleft individuals were compared with values of normal individuals reported by Lee. 28) The following conclusions were obtained; 1) The pattern of cranial base of the cleft subjects was almost the same as that previously reported for the normal individuals. 2) Anterio-posterior length of the mandible did not show any significant difference but in the cleft subjects, that of the males was larger than that of the females. 3) The maxilla of the cleft subjects was very retruded and showed very concave profile. 4) Gonial angle of the cleft subjects was very high, especially in the female clefts. 5) The height of ramus was very poor in the cleft subjects. 6) The facial length was almost the same, but the facial depth of the cleft subjects was smaller than that of the normal individuals. 7) Maxillary and mandibular incisors were severely retroclined. 8) The range of values in the cleft subjects was very variable and th female clefts showed more distured growth than the male clefts.
현성욱(Sung Wook Hyun),심인보(In-Bo Shim),김철성(Chul Sung Kim),강경수(Kyung-Su Kang),박주식(Chu-Sik Park) 한국자기학회 2008 韓國磁氣學會誌 Vol.18 No.1
We have prepared MnFe₂O₄ nanoparticles with polyol method. The crystallographic and magnetic properties were measured by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mossbauer spectroscopy. The high resolution transmission electron microscope (HRTEM) shows uniform nanoparticle-sizes with 6~8 ㎚. The crystal structure is found to be single-phase cubic spinel with space group of Fd3m. The lattice constant of MnFe₂O₄ nanparticles is determined to be 8.418 ± 0.001 A. Mossbauer spectrum of MnFe₂O₄ nanparticles at room temperature (RT) shows a superparamagnetic behavior. In VSM analysis, the diagnosis of the superparamagnetic behavior is also shown in hysteresis loop at RT. Mossbauer spectrum at 4.2 K shows that the well developed two sextets are with different hyperfine field H<SUB>hf</SUB>A = 498 (A-site) and H<SUB>hf</SUB>B = 521 (B-site) kOe.