• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.12-19
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• 1994

The crystallization behavior of the amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ alloy with isothermal annealing at $552^{\circ}C$ was studied by $M\"{o}ssbauer$ spectroscopy. The amorphous phase was revealed to coexist together with $Do_{3}-FeSi$ nanocrystalline and Cu-duster in annealed alloys by $M\"{o}ssbauer$ spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual armrphous, in spite of a slight change in the volume fraction of the FeSi and the residual armrphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and O.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.

• Journal of the Korean Magnetics Society
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• v.9 no.1
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• pp.29-34
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• 1999

$Y_{2.5}La_{0.5}Fe_5O_{12}$ is fabricated by a sol-gel method and the magnetic properties of single phase garnet are investigated by using X-ray diffraction, vibrating sample magnetometer, scanning electron microscopy and M$\"{o}$ssbauer spectroscopy. The single phase powders garnet was fired at 100$0^{\circ}C$ for 8 hours. The crystal structures of samples are cubic garnet. Mossbauer spectroscopy were measured from 13 K to 750 K. M$\"{o}$ssbauer spectra show that the iron exist ferric trivalence in sample. The spin wave constants were determined $B_{3/2}=0.32{\pm}0.05,\; C_{5/2}=0.18{\pm}0.05$ and Debye temperature were determined 382 K at 24(d) site and 246 K at 16(a)-site. The saturation magnetization $M_s$ of powder is 25 emu/g. 25 emu/g.

• Journal of the Korean Magnetics Society
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• v.20 no.5
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• pp.187-190
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• 2010

$Sn_{0.99}{^{57}Fe}_{0.01}O_2$ prepared by a sol-gel method, and studied by x-ray diffractometer, vibrating magnetometer, Superconducting quantum interference devices and M$\ddot{o}$ssbauer spectroscopy. the crystal structure were found to be a rutile tetragonal structure with space group $P4_2$/mnm, and oxygen deficiency are 5.6 % by Rietveld refinement. magnetization value were $M_s=1.95{\times}10^{-2}{\mu}_B/Fe$ at room temperature, and Curri-weiss temperature were and ${\theta}_{cw}$ = 18 k, measurement of VSM and SQUID, respectively. Mssbauer spectra of $Sn_{0.99}{^{57}Fe}_{0.01}O_2$ have been Sextet taken at various temperatures ranging from 4.2 K to RT, and isomer shift value $\delta$ = 0.18~0.36 mm/s of $^{57}Fe$ ion site all of the temperature range the state shows ferric.

• Journal of the Korean Magnetics Society
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• v.19 no.4
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• pp.152-155
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• 2009

Ba-Ferrite single crystals were prepared and the magnetic and thermal properties were characterized by Mossbauer spectroscopy. The single crystal layer was cut in the c-axis and radiated to the surface by ${\gamma}$-rays for Mossbauer spectroscopy. We found out that the spin states in Fe ions were parallel to the ${\gamma}$-rays direction and the whole crystal bulk formed only one crystal with the same spin direction. $M\"{o}ssbauer$ spectra in single crystal have only 4 sets of 4 absorption lines in each Fe site when the ${\gamma}$-rays have the same radiation direction with the c-axis in the crystal, and there was no 2b-site spectrum. The zero absorption of 2b-site means that there was a fast diffusion motion in a double-well atomic potential at room temperature, in which bipyramidal Fe ions have the two minima at each side mirror plane.

• Journal of the Korean Magnetics Society
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• v.5 no.1
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• pp.64-70
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• 1995

The authors have studied crystallographic and magrletic properties of $NdFe_{10.7}TiM_{0.3}(M=B,\;Ti)$ by X-ray diffraction, VSM magnetometer, and Mossbauer spectrometer. The Alloys were prepared by arc-melting under argon atmosphere. The $NdFe_{10.7}TiM_{0.3}$ has pure single phase, whereas the $NdFe_{10.7}Ti_{1.3}$ contains some $\alpha-Fe$, from powder X-ray diffractometry. The $NdFe_{10.7}TiM_{0.3}$ has the $ThMn_{12}$-type tetragonal structure with $a_{0}=8.587\;{\AA}\;and\;c_{0}=4.788\;{\AA}$. The Curie temperature ($T_c$) is $570{\pm}3\;K$ from $M\"{o}ssbauer$ spectroscopy performed at various temperatures ranging from 13 to 770 K. Each spectrum of below $T_c$ was fitted with five subspectra of Fe sites in the structure ($8i_{1},\;8i_{2},\;8j_{1},\;8j_{2}\;and\;8f$). The area fraction of the subspectra at room temperature are 16.4, 8.2, 14.8, 21.3 and 39.3 %, respectively. Magenetic hyperfine fields for the Fe sites decrease in the order, $H_{hf}(8i)>H_{hf}(8j)>H_{hf}(8f)$.

• 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.15 no.3
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• pp.167-171
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• 2005

Detailed aspects of the charge disproportionation (CD) transition for a polycrystalline $La_{1/3}Sr_{2/3}FeO_{2.96}$ were studied with the X-ray diffraction, $M\ddot{o}ssbauer$ spectroscopy, and SQUID magnetometer. The crystal structure was found to be rhombohedral with a space group R/3c. The lattice parameters were $a_R=5.4874\;\AA,\;and\;a_R=60.07^{\circ}$, respectively. $M\ddot{o}ssbauer$ spectra were taken within a wide range of temperature from 4.2 K up to room temperature. In the low temperature region, the spectra were comprised of two superimposed sextets which originated from $Fe^{3+}\;and\;Fe^{5+}$, respectively. This was the antiferromagnetic mixed valence state produced by the charges disproportionated into two different species. In the high temperature region, however, only a singlet from $Fe^{3.6+}$ was observed, indicating that it was a paramagnetic averaged valence state. The CD transition occurred in the temperature range from 175 K to 200 K, in which the two phases coexisted. The origin for the CD transition was explained by the thermally generated fast hopping of electrons. Hysteresis loop showed that there existed a strong antiferromagnetic interaction among magnetic ions. As the temperature increased thru the CD transition temperature, it was very likely that the interaction between $Fe^{3+}\;and\;Fe^{5+}$ was replaced by a more stronger one.

• Journal of the Korean Magnetics Society
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• v.6 no.6
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• pp.397-404
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• 1996

The magnetic properties of $Ni_{1-x}Zn_{x}Fe_{2}O_{4}$ have been studied by X-ray diffractometry and $M\"{o}ssbauer$ Spectroscopy at room temperature. The X-ray diffraction study show that spinel structure is formed in all x, lattice constants linearly increased from $8.3111{$\AA$}~8.4184{$\AA$}({\pm}0.0003)$ with increasing x from 0 to 1, and oxygen parameter increase with increasing x. $M\"{o}ssbauer$ spectrum shows that $Ni_{1-x}Zn_{x}Fe_{2}O_{4}(x=0)$ has two antiparallel magnetic structure due to $Fe^{3+}$ octahedral site and $Fe^{3+}$ tetrahedral site. $Ni_{1-x}Zn_{x}Fe_{2}O_{4}$ with $0.2{\leq}x{\leq}0.6$ has magnetic structure of Yafet and Kittel, in particularly, specimen with x=0.6 shows relaxation effect. Specimen with $x{\geq}0.8$ show paramagnetic quadrupole splitting. The isomer shift is independent of x, but quadrupole splittings decrease with increasing x in the range of $0.8{\leq}x{\leq}1$, and nuclear magnetic fields decrease with in¬creasing x in the range of $0{\leq}x{\leq}0.6$. The magnetic properties of $Ni_{1-x}Zn_{x}Fe_{2}O_{4}$ change from ferrimagnetics to pararnagnetics with increasing x.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.18-21
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• 2007

The hexagonal $HoMn_{1-x}-Fe_xO_3$(x=0.00, 0.05) thin films were prepared using pulsed laser deposition(PLD) method on $Pt/Ti/SiO_2/Si$ substrate. The microstructure and magnetic properties have been studied by x-ray diffraction(XRD), atomic force microscopy (AFH), scanning electron microscope(SEM:), x-ray photoelectron spectroscopy(XPS), and conversion electron $M\"{o}ssbauer$ spectroscopy(CEMS). From the analysis of the x-ray diffraction patterns, the crystal structure for all films was found to be a hexagonal($P6_3cm$), which was preferentially grown along(110) direction. The lattice constant $c_0$ of the film with x=0.05 was close to that of single crystal, whereas lattice constant $a_0$ with respect to single crystal shows a slight decrease. This difference of lattice parameters between film and single crystal was caused by the lattice mismatch between the film and $Pt/Ti/SiO_2/Si$ substrate. Conversion electron $M\"{o}ssbauer$ spectrum of $HoMn_{0.95}Fe_{0.05}O_3$ thin film shows an asymmetry doublet absorption ratio at room temperature, which is due to the oriented direction of crystallographic domains. This is corresponding with analysis of x-ray diffraction. The quadrupole splitting(${\Delta}E_Q$) at room temperature is found to be $1.62{\pm}0.01mm/s$. This large ${\Delta}E_Q$ was caused by asymmetry environment surrounding Fe ion.

• Korean Journal of Materials Research
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• v.28 no.7
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• pp.371-375
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• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.