• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.73.1-73.1
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.138-139
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• 2004

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.10a
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• pp.118-118
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• 2003

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.67-73
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• 1998

Crystallographic and magnetic properties of perovskite $Gd_{1-x}Sr_xFeO_{3-y}$ (x=0.0, 0.5) substituted $Sr^{2+}$ having larger inoic radius than $Gd^{3+}$ at GdFeO$_3$have been studied by x-ary diffraction, M$\ "{o}$ssbauer spectroscopy, and VSM. The cystal structures are found to be orthorhombic with the lattice parameters : $a_o=5.53\;{\AA},\;b_o=5.608\;{AA},\;C_o=7.724\;{\AA}$ for $Gd_{0.5}Sr_{0.5}FeO_{3-y}$ (x=0.0, 0.5) have been investigated over temperature range from 4.2 to 690 K using the M$\ "{o}$ssbauer technique. The Neel temperatuer of $Gd_{1-x}Sr_xFeO_{3-y}$ system is 690 K with x value of 0.0 and 515 K with x value of 0.5. Analysis of M$\ "{o}$ssbauer spectra Mohr's salt analysis for $Gd_{1-x}Sr_xFeO_{3-y}$ demonstrated the existence of the mixed valence states of iron and the coordination state of $Fe^{3+}$ and $Fe^{4+}$ ions. The Corresponding hyperfine parameters for GdFeO$_3$ are compatible with S=5/2 $Fe^{3+}$ in octahedral cooedination.l cooedination.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.342-348
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• 1993

At 1473 K under atmospheric pressure, the homogeneous samples of the $Sm_{1-x}Sr_xFe^{3+}{_{1-t}}Fe^{4+}{_t}O_{3-y}$ ($0.00{\leq}x{\leq}1.00$) ferrite system were prepared. With the increase in x value, the amount of $Fe^{4+}$ ion increased and the crystallographic structure was changed from orthorhombic symmetry to cubic symmetry. The electrical conductivity at constant temperature sharply increases and the activation energy decreases with the increase of $Fe^{4+}$ ion. $M{\ddot{o}}ssbauer$ spectrum of the sample x=0.00 shows six-line pattern indicating the presence of $Fe^{3+}$ ion in the octahedral sites.

• 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.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.17 no.1
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• pp.38-42
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• 2007

The crystallographic and magnetic properties of $KFeO_2$ powder prepared by ball-mill method, have been studied by x-ray diffraction(XRD), $M\"{o}ssbauer$ spectroscopy, and vibrating sample magnetometer(VSM) measurements. The crystal structure of $KFeO_2$ powder at room temperature is determined to be an orthorhombic structure of Pbca with its lattice constants $a_0=5.557{\AA},\;b_0=11.227{\AA},\;c_0=15.890{\AA}$ by Rietveld refinement. $M\"{o}ssbauer$ spectra of $KFeO_2$ were taken at various temperatures ranging from 4.2 to 818 K. The magnetic hyperfine field and isomer shift value at 4.2 K and RT were 519 kOe, 489 kOe and 0.19 mm/s, 0.05 mm/s respectively. The average hyperfine field $H_{hf}(T)$ of the $KFeO_2$ shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.36(T/T_N)^{5/2}$ for $T/T_N$<0.7, indicative of spin-wave excitation.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.3-7
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• 2001

$M\"{o}ssbauer$ spectra of the $Ni_{1+x}Ti_xFe_{2-2x}O_4$ systems ($0{\leqq}x{\leqq}0.7$), which appear as single phase spinel structure, were examined at RT. The $M\"{o}ssbauer$ spectra reveal two sextet for $0{\leqq}x{\leqq}0.3$, two sextet and a doublet for $0.4{\leqq}x{\leqq}0.6$, and a doublet for x=0.7 As x increases, the area ratio of B-site and A-site($A_B/A_A$) of the sextet decreases, and the area ratio of the doublet and the total areas($A_{doublet}/A_{tot.}$) increases. The isomer shift(I.S.) of A-site slightly increases and magnetic hyperfine fields($H_{hf}$) of two sites decrease as the increasing x. From these results, we have obtained the cation distributions of the samples and concluded that the increasing x leads to the decrease of covalency of $Fe^{3+}-O^{2-}$ bond in A-sites and A-B superexchange interactions.eractions.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.859-862
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• 2001

The crystal structure and magnetic properties of the $Ni_{1-x} Cd_xFeAlO_4$(0$\leq$x$\leq$0.5) have been investigated by means of X-ray diffractometry and Mossbauer spectroscopy. The samples($0\leq$x$\leq$0.5) have been prepared by the ceramic sintering method. The X-ray diffraction pattern shows that the crystal structure of the samples is a cubic spinel type. The lattice constant has been found by extrapolation using the Nelson- Riley function and it increases slightly from $8.321{\AA}$ to $8.410{\AA}$ with Cd concentration. The Mossbauer spectra for x<0.4 show a superposition of two sextets and a paramagnetic doublet at room temperature. The cation distribution for x=0 was determined to be $[Fe_{0.75}Al_{0.25}]^A[NiFe_{0.25}Al_{0.75}^BO_4$. The superparamagnetic doublet for x< 0.4 seems to be due to A1 ion in tetrahedral site by the superparamagnetic clustering effect.