• Journal of Magnetics
• /
• v.19 no.4
• /
• pp.323-326
• /
• 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.

• Journal of the Korean Magnetics Society
• /
• v.21 no.1
• /
• pp.5-9
• /
• 2011

M$\ddot{o}$ssbauer and Raman spectrum studies have been carried out on the 2b-site Fe ion in the Ba-ferrite (M-type). The thermal dynamics of Fe ion was analyzed by M$\ddot{o}$ssbauer spectra at different angles between the $\gamma$-ray direction and c-axis. The vibration on the 2b-site was more active compare to other direction and had very strong intensity in the Raman spectrum.

• Journal of the Korean Magnetics Society
• /
• v.20 no.4
• /
• pp.153-159
• /
• 2010

Magnetic properties of basic rocks samples distributed in the seaside area of Ulleung island were investigated by means of X-ray fluorescence spectroscopy (XRF), M$\ddot{o}$ssbauer spectroscopy and SQUID magnetometer. We found that samples were typical basic rock which had the total amount of iron compounds varies from 10.6 wt% to 14.5 wt% depending on the different regions by XRF. The M$\ddot{o}$ssbauer spectra and magnetic hysteresis behaviors of the samples show ferromagnetic properties due to hematite. Also, temperature dependences of magnetization at applied magnetic field of 1 T for samples show magnetic transitions at 41 K~60 K.

• Journal of the Korean Magnetics Society
• /
• v.25 no.5
• /
• pp.169-173
• /
• 2015

Fe compounds of volcanic basalt samples distributed at the Hantan riverside in Cheorwon were investigated by means of X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF) and $M{\ddot{o}}ssbauer$ spectroscopy. We found that samples were typical basic rock which consisted of augite, anorthite, albite and sanidine etc. They had the total amount of iron compounds including hematite (${\alpha}-Fe_2O_3$) varies from 6.20 w% to 12.8 w% depending on the different regions by XRF. The $M{\ddot{o}}ssbauer$ spectra of the samples were consisted of three doublets. The balance state of Fe ions of all samples were chiefly $Fe^{2+}$, and $Fe^{2+}/Fe^{3+}$ ratios were 2.27~3.42.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2004.12a
• /
• pp.217-218
• /
• 2004

• Journal of Magnetics
• /
• v.7 no.2
• /
• pp.40-44
• /
• 2002

Crystallographic and magnetic properties of ;$LaFe_{1-x}Ga_xO_3$($\chi$= 0, 0.1, 0.3, 0.5, and 0.7) were studied using XRD and Mossbauer spectroscopy. The crystal structures were found to be orthorhombic and the lattice parameters $\alpha$, b, and c were found to decrease with increasing Ga substitution. M$\ddot{o}$ssbauer spectra were obtained at various absorber temperatures ranging from 20 K to 750 K. The M$\ddot{o}$ssbauer spectra were all sextets below $T_N$ and were all singlets above $T_N$. Asymmetric broadening of the M$\ddot{o}$ssbauer spectral lines at 20 K was explained by the multitude of possible environments for an iron nucleus. As the temperature increases to $T_N$, a systematic line broadening in M$\ddot{o}$ssbauer spectra was observed and interpreted to originate from different temperature dependencies of the magnetic hyperfine fields at various iron sites.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.3
• /
• pp.183-190
• /
• 2000

The purpose of this study is to evaluate the magnetic property change of the nuclear reactor vessel steel irradiated by fast neutrons using $M{\ddot{o}}ssbauer$ spectroscopy, and the effects of the defects produced by neutron irradiation on the changes using X-ray diffraction. The specimens, fabricated with the dimension of $23mm{\times}18mm{\times}70{\mu}m$, were irradiated by neutron fluence from $10^{12}n/cm^2\;to\;10^{18}n/cm^2$ at 343K. Throughout the experiments, it is understood that (1) the X-ray diffraction measurement shows that the change of crystal nature is started at the irradiation of $10^{16}n/cm^2$ and a crystal structure has been severely damaged at the irradiation over $10^{17}n/cm^2$, (2) the analysis of the $M{\ddot{o}}ssbauer$ spectra has shown that magnetic transition phenomena occur at the irradiation over $10^{17}n/cm^2$ and (3) both methods can be utilized as nondestructive test methods for the embrittlement evaluation of materials irradiated by fast neutrons.

• Journal of Magnetics
• /
• v.20 no.1
• /
• pp.26-30
• /
• 2015

The crystallographic and magnetic properties of gallium-substituted cobalt ferrite ($CoGa_xFe_{2-x}O_4$) were investigated. The new material was synthesized using conventional ceramic methods, with gallium substituted for ferrite in the range of x = 0.0 to 1.0, in steps of 0.2. X-ray diffraction and M$\ddot{o}$ssbauer spectroscopy were used to confirm the presence of crystallized particles in the $CoGa_xFe_{2-x}O_4$ ferrite powders. All of the samples exhibited a single phase with a spinel structure, and the lattice parameters decreased as the gallium content increased. The particle size of the samples also decreased as gallium increased. For $x{\leq}0.4$, the M$\ddot{o}$ssbauer spectra of $CoGa_xFe_{2-x}O_4$ could be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe^{3+}$ with A- and B-sites. However, for $x{\geq}0.6$, the M$\ddot{o}$ssbauer spectra could be fitted with two Zeeman sextets and one doublet. The variation in the M$\ddot{o}$ssbauer parameters and the absorption area ratio indicated a cation distribution of $(Co_{0.2-0.2x}Ga_xFe_{0.8-0.6x})[Co_{0.8+0.2x}Fe_{1.2-0.4x}]O_4$, and the magnetic behavior of the samples suggested that the increase in gallium content led to a decrease in the saturation magnetization and in the coercivity.

• Journal of Radiation Protection and Research
• /
• v.28 no.3
• /
• pp.183-187
• /
• 2003

Collimator for $M{\ddot{o}}ssbauer$ source was manufactured for compton scattering experiment. Exposure dose rate was calculated and measured using GM counter for radiation evaluation. These results were well agreed to each other and used for collimator design. SUS303 was used for collimator material because exposure dose rate at 10 cm is about 2 mR/h. The radiation emited from the 35 mm, 65 mm hole was measured using gamma camera which have 4' diameter. 2-D radiation image was acquired and analyzed. The radiation size at Gamma Camera was 8.0 mm and 5.8 mm respectively.

• Journal of Magnetics
• /
• v.14 no.2
• /
• pp.86-89
• /
• 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.