• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.1-6
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• 2002

Al$\^$3+/ substituted garnet Y$_3$Fe$\_$5-x/Al$\_$x/O$\_$12/ (x=0.0, 0.25, 0.5, 0.75, 1.0) was fabricated by sol-gel method. The crystallographic and magnetic properties of Y$_3$Fe$\_$5-x/Al$\_$x/O$\_$12/ have been studied with Mossbauer spectroscopy, x-ray diffraction (XRD), thermogravimetry analysis (TGA), differential thermal analysis (DTA), and vibrating samples magnetometer (VSM). The crystal structure of Y$_3$Fe$\_$5/O$\_$12/ is found to be a cubic with the lattice constant a$\_$0/= 12.381$\pm$0.005 $\AA$. The lattice constants a$\_$0/ decreases linearly from 12.381 to 12.304 A as the Al concentration (x) increases from x=0.0 to 1.0. Mossbauer spectra of measured at Y$_3$Fe$\_$5-x/A1$\_$x/O$\_$12/ various absorber temperatures of 13 to 600 K. Mossbauer spectrum for x = 0.0 is consist of well resolved two sets of six line patterns. While with increasing Al concentration outer sextet patters, which is originating from octahedral sites, broadens widely. These phenomena are interpreted in terms of random probability distributions of Fe$\^$3+/ and Al$\^$3+/ in tetrahedral site.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.14-17
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• 2006

[ $AIFeO_3$ ]has been studied by x-ray diffraction (XRD), vibrating sample magnetometer, Mossbauer spectroscopy. The crystal structure is found to orthorhombic with the lattice parameters being $a_0=4.983\;{\AA},\;b_0=8.554\;{\AA},\;c_0=9.239\;{\AA}$, Magnetic hysteresis curve for $AIFeO_3$ showed weakly ferromagnetic phase at room temperature and a asymmetric shape dependent on the direction of applied field at low temperature. The Curie temperature determined by the temperature dependence of magnetization is 250 K. Mossbauer spectra of $AIFeO_3$ have been taken from 4.2 K to 295 K. Isomer shift at room temperature are found to be $0.11\~0.32\;mm/s$, which is consistent with ferric state. The absorption lines widths become broader with increasing temperature, which is attributed to the Fe ions distribution of each cation site and anisotropy energy difference of each sublattice.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.51-59
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• 2006

$M\"{o}ssbauer$ spectroscopy is one of the very powerful analytical methods for studying the steel properties. It is the most important advantage that the steel properties can be quantitatively analyzed by Mossbauer analysis. The quantitative analysis could provide various information about corrosion products, environmental condition, kind of steel, foreign element, particle size, etc. It can be also applied for the study of strength and phase of steel, as functions of the kind of steel and foreign elements.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.43-48
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• 2013

The Jahn-Teller distortion of chalcogenide $Fe_{0.9}M_{0.1}Cr_2S_4$ (M=Co, Ni, Zn) have been investigated by M$\ddot{o}$ssbauer spectroscopy. The crystal structures of $Fe_{0.9}M_{0.1}Cr_2S_4$ (M=Co, Ni, Zn) are cubic spinel at room temperature. Magnetoresistance measurements indicate these system is conducting-semiconducting transistion around $T_C$. Below $T_C$, the asymmetric line broadening is observed and considered to be dynamic Jahn-Teller distortion. Isomer shift value of the samples at room temperature was about 0.5 mm/s, which means that charge state of Fe ions is ferrous in character. The Ni substitutions for Fe occur to increase the Jahn-Teller relaxation. CMR properties could be explained with magnetic polaron due to Jahn-Teller effect, which is different from both the double exchange interactions of manganite system and the triple exchange interactions of chalcogenide $Cu_xFe_{1-x}Cr_2S_4$.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.226-230
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• 2003

In this study, we analyzed the volcanic rock and scoria samples taken from special sites of Jeju island in two ways at the room temperature. One is the analysis of the chemical composition using X-ray fluorescence spectrometer, the other is the analysis of minerals in the samples, oxidized iron's genus, valence state and magnetic properties using X-ray diffractometry and Mossbauer spectroscopy. We believe that the volcanic rock and scoria samples are chiefly made of silicate minerals, like SiO$_2$, and they also have olivine, pyroxene, ilmenite, hematite and magnetite. The major Fe fractions of the volcanic rock samples are 2+ charge state and those of the scoria samples are 3+ charge state.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.76-80
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• 2007

Three nano-sized Fe-N particle samples synthesized by Chemical Vapor Condensation (CVC) were analyzed using $M\"{o}ssbauer$ spectroscopy, XRD and BET. The synthesized nanoparticles consisted of ${\epsilon}-Fe_{2.12}N,\;{\gamma}'-Fe_4N,\;{\alpha}-Fe\;and\;{\gamma}-Fe.\;{\gamma}'-Fe_4N$ was mainly formed at the low decomposition temperature. With increasing decomposition temperature, the phase was changed to ${\gamma}-Fe$ via ${\epsilon}-Fe_{2.12}N$. For synthesizing Fe-N phases, this study implies that the low decomposition temperature is better than high temperature during Chemical Vapor Condensation.

• Journal of the Korean Magnetics Society
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• v.16 no.2
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• pp.144-148
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• 2006

$CoGa_{0.1}Fe_{1.9}O_4$ nanoparticles have been prepared by a sol-gel method. The structural and magnetic properties have been investigated by XRD, SEM, VSM and $M\ddot{o}ssbauer$ spectroscopy. $CoGa_{0.1}Fe_{1.9}O_4$ powder that was annealed at $250^{\circ}C$ has spinel structure and behaved superparamagnetically. The estimated size of superparammagnetic $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle is around 10 nm. The hyperfine fields at 4.2 K f3r the A and B patterns were found to be 518 and 486 kOe, respectively. The blocking temperature $(T_B)$ of superparammagnetic $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle is about 250 K. The magnetic anisotropy constant of $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle was calculated to be $3.0X10^5\;ergs/cm^3$. $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle was annealed at $250^{\circ}C$ will be used to candidate for biomedicine applications as magnetic carriers.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.37-41
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• 2012

The Ag nanoparticles attached $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ (LSCF) perovskites were prepared by plasma method. The Ag nanoparticles with size of several nanometers deposited from the Ag target were coated on the surface of LSCF powders with size range from 0.2 to 3 ${\mu}m$. The agglomeration of Ag particles annealed at $800^{\circ}C$ under inert gas of Ar were rarely observed. The inter-diffusion between surface Ag and core LSCF is effectively strong to prevent aggregation of Ag nanoparticles. The wave number of FT-IR spectra for LSCF were largely shifted as the concentration of Ag on LSCF up to 2.11 wt.%. The ionic states of irons in LSCF were measured by M$\ddot{o}$ssbauer spectroscopy. The small amount of $Fe^{4+}$ ions are converted to $Fe^{3+}$ ions after Ag nanopartcles were coated on LSCF.

• Journal of the Korean Magnetics Society
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• v.24 no.2
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• pp.41-45
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• 2014

By M$\ddot{o}$ssbauer spectroscopy and x-ray measurement $(Fe_{0.95}Ni_{0.05})_7Se_8$ has been studied. The crystal structure of $(Fe_{0.95}Ni_{0.05})_7Se_8$ is found to be a triclinic superstructure of the NiAs sturcture while $Fe_7Se_8$ has a orthohexagonal superstructure. Abrupt changes of quadrupole shifts near 125 K for $(Fe_{0.95}Ni_{0.05})_7Se_8$ suggests that the spin-rotation transition proceeds abruptly, in contrast with the gradual transition reported for $Fe_7Se_8$ with a triclinic superstructure. Isomer shifts indicate a ferrous state for the iron ions at all four states.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.231-236
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• 2003

The $Al_{0.2}$CoF $e_{1.8}$ $O_4$ferrite powders have been prepared by the sol-gel method. The crystallographic and magnetic properties of the sample depending on annealing temperature have been investigated by means of x-ray diffraction, FE SEM, Mossbauer spetroscopy and vibrating sample magnetometry. The x-ray diffractions of all samples annealing temperature above 873 K clearly indicate the presence of spinel structure, the lattice constant decrease from 8.425 $\AA$ at 873 K to 8.321 $\AA$ at 1073 K, whereas the particle size rapidly increase from about 39 nm at 673 K to about 108 nm at 1073 K. The Mossbauer spectra annealed above 873 K could be fitted as the superposition of two sextets due to F $e^{3+}$ at A-site and B-site. The isomer shift (IS) and quadruple splitting (QS) values nearly constant with annealing temperature, whereas magnetic hyperfine field ( $H_{hf}$) of A-site slowly in crease and that of B-site fastly increases with increasing annealing temperature. The magnetic behaviour of powders shows that the saturation magnetization increase from 0.7 emu/g at 473 K to 72.1 emu/g at 1073 K while the coercivity decrease from 0.951 kOe at 673 K to 0.374 kOe at 1073 K with increasing annealing temperature.