• Journal of Magnetics
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• 제19권4호
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• pp.323-326
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• 2014

Superparamagnetic maghemite nanoparticles were prepared by chemical co-precipitation, followed by a temperate oxidation stage, and investigated using FE-SEM, XRD, TGA, VSM, and M$\ddot{o}$ssbauer spectroscopy. Through SEM image and XRD analysis, its average particle size was found to be 13.9 nm. While VSM magnetic measurement showed typical superparamagnetic behavior at room temperature, M$\ddot{o}$ssbauer spectroscopic investigation revealed that non-vanishing magnetic hyperfine structure were retained. Cation distribution estimated from M$\ddot{o}$ssbauer spectroscopy confirmed the formation of maghemite nanophase in the sample.

• 대한토목학회논문집
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• 제26권1B호
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• pp.107-111
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• 2006

2종류의 제철 반응조에 있어서, 각종의 반응조건 하에 생성한 산화철을 x-ray회절과 M$\ddot{o}$ssbauer spectroscopy실험으로 철산화 물질을 동정한 결과, 여재 표면에 부착한 철 산화물의 결정은 pH 조건에 관계없이 Ferrihydrite($Fe_5HO_8{\cdot}4H_2O$)이었으며, Batch(회분) 실험에서 생긴 철 산화 물질은 가수분해에 의해 생긴 것으로, Microcrystalline Goethite 이었다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
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• pp.217-218
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• 2004

• 한국재료학회지
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• 제21권8호
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• pp.439-443
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• 2011

The crystal structure and magnetic properties of a new solid solution type ferrite $(Fe_2O_3)_5-(Al_2O_3)_{3.4}-(Ga_2O_3)_{0.6}-SiO$ were investigated using X-ray diffraction and M$\"{o}$ssbauer spectroscopy. The results of the X-ray diffraction pattern indicated that the crystal structure of the sample appears to be a cubic spinel type structure. The lattice constant (a = 8.317 ${\AA}$) decreases slightly with the substitution of $Ga_2O_3$ even though the ionic radii of the Ga ions are larger than that of the Al ions. The results can be attributed to a higher degree of covalency in the Ga-O bonds than in the Al-O and Fe-O bonds, which can also be explained using the observed M$\"{o}$ssbauer parameters, which are the magnetic hyperfine field, isomer shift, and quadrupole splitting. The drastic change in the magnetic structure according to the Ga ion substitution in the $ (Fe_2O_3)_5(Al_2O_3)_{4-x}(Ga_2O_3)_xSiO$ system and the low temperature variation have been studied through a M$\"{o}$ssbauer spectroscopy. The M$\"{o}$ssbauer spectrum at room temperature shows the superpositions of two Zeeman patterns and a strong doublet. It shows significant departures from the prototypical ferrite and is comparable with the diluted ferrite. The doublet of spectrum at room temperature appears to originate from superparamagnetic clusters and also the asymmetry of the doublet appears to be caused by the preferred orientation of the crystallites. The M$\"{o}$ssbauer spectra below room temperature show various complicated patterns, which can be explained by the freezing of the superparamagnetic clusters. On cooling, the magnetic states of the sample were various and multi critical.

• Journal of Magnetics
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• 제2권4호
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• pp.116-122
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• 1997

To determine whether there is an ionic substitution of Ni, Co, Mn, and Al for Fe in synthetic goethites these materials have been studied by M$\ddot{o}$ssbauer spectroscopy at various temperatures ranging from 77 to 400 K. It is found that the presence of substituting elements in magnetically ordered structure of crystals may change the shape of M$\ddot{o}$ssbauer spectra of these caterials. The approximate distribution function of the effective magnetic field in the Fe nucleus p(Hn) is obtained from the M$\ddot{o}$ssbauer spectra. It is noted that the mean value of p(Hn) and its integral width can be taken as a measure of substitution in goethites.

• Journal of Magnetics
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• 제14권2호
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• pp.93-96
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• 2009

The Mn-substituted M-type Ba-ferrite ($BaFe_{12-x}Mn_xO_{19}$; x = 0, 2, 4, 6) powders were prepared by the HTTD (High Temperature Thermal Decomposition) method. The effect of $Mn^{3+}$ Jahn-Teller ions on the magnetic properties has been studied by x-ray diffraction, vibrating sample magnetometry, and $M{\ddot{o}}ssbauer$ spectroscopy. With increasing Mn substitution, the lattice parameter $a_0$ increases while $c_0$ decreases. The magnetocrystalline anisotropy constants ($K_1$) were determined as 2.9, 2.2, 1.8, and, $1.3{\times}10^6\;erg/cm^3$ for x = 0, 2, 4, and 6, respectively, by the LAS method. We have studied the change of cation distribution by $M{\ddot{o}}ssbauer$ spectroscopy which is closely related to $K_1$.

• Journal of Magnetics
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• 제14권2호
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• pp.86-89
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• 2009

Structural and magnetic properties of polycrystalline $CaFe_2O_4$ prepared by the solid state reaction method were studied using powder X-ray diffraction (XRD) and $M{\ddot{o}}ssbauer$ spectroscopy. The structure of $CaFe_2O_4$ belongs to an orthorhombic system (space group: Pnma) with the lattice parameters $a=9.2373\;{\AA}$, $b=3.0237\;{\AA}$, and $c=10.7124\;{\AA}$. Results of structural refinement indicate, however, that there are two slightly different iron sites in the sample. The $M{\ddot{o}}ssbauer$ spectrum at 4.2 K shows a hyperfine sextet with a hyperfine magnetic field and an isomer shift of 47.3 T and 0.36 mm/s, respectively. An examination of the spectrum revealed that the line widths of the spectral lines were not uniform. The degree of asymmetric line broadening decreases with increasing temperature, suggesting that the difference in the degree of crystalline distortions between two $FeO_6$ octahedra is eliminated as the temperature rises.

• 한국재료학회지
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• 제18권3호
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• pp.143-147
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• 2008

Fe compounds in scoria as distributed in the south-western area of Jeju Island were investigated using X-ray fluorescence spectroscopy, X-ray diffractometry, and $^{57}Fe$ $M{\ddot{o}}ssbauer$ spectroscopy. The samples were prepared from four parasite volcanoes. It was found that these samples are typical basalt comprised of $SiO_2$, $Al_2O_3$, Fe, and silicate minerals. The $M{\ddot{o}}ssbauer$ spectra showed doublets for olivine, pyroxene, and ilmenite as well as sextets for hematite and magnetite. The valence state of Fe is chiefly a 3+ charge state with a slight 2+ charge state. It is expected that these results will add to the body of information related to the formation mechanisms of Jeju Island.

• 한국전기전자재료학회논문지
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• 제11권1호
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• pp.62-66
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• 1998

M$\ddot{o}$ssbauer spectra of ferrimagnetic $Fe_2SE_8$ prepared with $^{57}Fe$ enriched iron have been taken at 298 K and below 78K, and Fe\ulcornerSe\ulcorner has been studied by X-ray diffraction. The crystal structure is found to be a "3c" hexagonal superstructure of the NiAs structure. Three sets of six-line hyperfine patterns were obtained and assigned to three magnetically nonequivalent sites of a superstructure of the crystal. The iron ions at all three sites are found to be in a highly covalent ferrous state. It is shown that the results obtained at the low temperature region are well consistent with Okazaki's "3c" superstructure model.uperstructure model.

• 한국자기학회지
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• 제20권4호
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• pp.153-159
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• 2010

울릉도의 해안지역에서 염기성암 시료에 대하여 X-선 형광 분광 분석, M$\ddot{o}$ssbauer 분광 분석 및 SQUID 분석으로 물리적 특성을 조사하여 화산암의 화학적 조성과 시료 내에 존재하는 Fe의 원자가 상태와 자기적 성질을 연구하였다. 울릉도 해안지역의 염기성암은 알칼리 장석 계열의 광물들이 주 광물로 구성되어 있으며, 적철석인 hematite(${\alpha}-Fe_2O_3$)을 포함한 총 Fe 화합물의 중량비는 10.6~14.5 wt%의 범위에 있음을 알 수 있었다. M$\ddot{o}$ssbauer spectrum과 자기이력 곡선을 조사한 결과로 부터 모든 시료들의 자기적 성질이 hematite(${\alpha}-Fe_2O_3$)에 의한 강자성을 나타내고 있음을 알 수 있었다. 또한 10 K~350 K 온도 범위에서 외부 자기장인 +1 T를 인가하고 온도에 따른 자기화의 변화를 측정한 결과로부터 41 K~60 K 사이의 온도에서 시료들의 자기전이가 나타나고 있음을 알 수 있었다.