• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.232-236
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• 1997

We have gone into details about the velocity calibration of sinusoidal mode for Mossbauer spectrometer. Since sinusoidal Mossbauer spectrometer has a ${\gamma}$-ray source that oscillates at the end of loudspeaker with the natural frequency. Doppler velocity is accurate and stable. From the analyzing Mossbauer spectra of $Fe_3O_4$ and U $Fe_3O_4$ (unbalanced $Fe_3O_4$), we have shown the power of correct velocity for sinusoidal mode.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1107-1112
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• 1996

Ni를 Cd로 대치시켜 세라믹 소결법으로 합성한 Ni0.8Cd0.2Fe2O4 의 X-ray 회절선을 측정하여 구조를 확인하고, 형성된 결정체의 격자 상수를 조사하였다. 이 시료의 Mossbauer 스펙트럼을 80K-900K의 온도 영역에서 측정 분석하여 Mossbauer parameter의 온도 의존성과 Fe 이온에 대한 자료를 얻고, 이 자료를 토대로 Ni0.8Cd0.2Fe2O4 의 자기 전이 현상과 Curied 온도 Tc와 격자 비열 및 Debye 온도와 같은 물성을 조사하였다.

• Proceedings of the Korean Magnestics Society Conference
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• 1994.10a
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• pp.34-35
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• 1994

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.186-187
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• 2003

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.118-124
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• 1998

$Ni_{0.65}Zn_{0.35}Cu_{0.1}Fe{1.9}O_4$ has been studied with Mossbauer spectroscopy and X-ray diffraction. The crystal structure is found to be a cubic spinel with the lattice constant $a_0=8.390{\AA}$. Mossbauer spectra of $Ni_{0.65}Zn_{0.35}Cu_{0.1}Fe{1.9}O_4$ has been taken at various temperatures ranging from 12 K to 705 K. The isomer shift indicates that iron ions are ferric at tetrahedral [A] and octahedral sites [B], respectively. The Neel temperature is determined to be $T_N=705\;K$. As the temperature increases toward $T_N$ a systematic line broadening effect in the Mossbauer spectrum is observed and interpreted to originate from different temperature dependencies of the magnetic hyperfine fields at various iron sites. The quadrupole splitting just on $T_N$ is 0.41 mm/s whereas the quadrupole shift below $T_N$ vanishes. This implies that the orientation of the magnetic hyperfine field with respect to be principal axes of the electric field gradient is random.

• Korean Journal of Materials Research
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• v.9 no.7
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• pp.701-706
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• 1999

The crystal structure and magnetic properties of magnetic oxide system (F $e_2$ $O_3$)$_{5}$(A $l_2$ $O_3$)$_{4-x}$(G $a_2$ $O_3$)$_{x}$)SiO has been studied using X-ray diffraction and Mossbauer spectroscopy The changes of magnetic structure by the Ga ion substitution and the temperature variation have been investigated using Mossbauer spectroscopy, and the results are compared with those of the SQUIB measurements. Results of X-ray diffraction indicated that the crystal structures of the system change from a cubic spinel type to an orthorhombic via the intermediate region. This magnetic oxide system seems to be new kind of spinel type ferrites containing high concentration of cation vacancies. Various and complicated Mossbauer spectra were observed in the samples (x>0.2) at temperatures lower than room temperature. This result could be explained by freezing of the superparamagnetic dusters. On cooling and substitution, magnetic states of the system show various and multicritical properties. Unexpected dip in magnetization curves below 50K was observed in SQUID measurements. It was interpreted as an effect of spin canting including spin freezing or collective spin behavior.ior.r.

• 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.8 no.4
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• pp.203-209
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• 1998

Crystallographic and magnetic properties of single phase garnet $Y_{3-x}Bi_xFe_5O_{12}$ (x=0.0, 0.25, 0.5, 0.75, 1.0) were studied by using x-ray diffraction, Mossbauer spectroscopy and vibrating sample magnetometer (VSM). Ultra-fine polycrystalline cubic samples have been prepared by sol-gel method. The lattice constant increase linearly with increasing an amount of Bi. Annealing temperature was larger than 800 $^{\circ}C$ for the growth of a single-phase garnet powder. The second phase of garnet, $(BiFeO_3)$, was at 1000 $^{\circ}C$ for x=0.75, and 950 $^{\circ}C$ for x=1.00. From Mossbauer spectroscopy and VSM measurements, the magnetization and the coercivity were decreased and the Curie temperature $Y_{3-x}Bi_xFe_5O_{12}$(x=0.0, 0.25, 0.5, 0.75, 1.0) was slightly increased as increasing the Bi content.

• Journal of the Korean Magnetics Society
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• v.9 no.1
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• pp.17-22
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• 1999

Hexagonal M-type barium ferrite $BaFe_{12}O_{19}$ was prepared by a direct solid state reaction between $BaCO_3$ and ${\Alpha}-Fe_2O_3$ powders at temperatures ranging from 800 to 1000 $^{\circ}C$ in a nitrogen or air environment. The effects of NaCl on phase transformation of mixture of $BaCO_3$ and ${\Alpha}-Fe_2O_3$ to $BaFe_{12}O_{19}$ were studied using X-ray diffraction and M$\"{o}$ssbauer spectroscopy. Regardless of the environment for heat treatment or the added NaCl, two phases, BaFe and ${\Alpha}-Fe_2O_3$, coexist for samples heat treated at 800 $^{\circ}C$, but a single phase was observed from samples heat treated at 100$0^{\circ}C$ in both air and nitrogen environments. It was found that the addition of NaCl reduced the amount of $a-Fe_2O_3$ phase.hase.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.16-21
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• 2000

Magnetic properties and crystallographic properties of $Cu_{0.95}Ge_{0.95}Fe_{0.1}O_3$ were studied by using x-ray diffraction, superconducting quantum interference device (SQUID) and Mossbauer spectroscopy. Our sample has orthorhombic structure and the lattice constants are a = 4.795 $\AA$, b = 8.472 $\AA$, c = 2.932 $\AA$. The spin-Peierls (SP) transition temperatures of our sample is 13 K. The Mossbauer spectra consisted with two Zeeman sextets and one doublet due to $Fe^{3+}$ions. The Zeeman sextets come from tetrahedral $Fe^{3+}$ions and the doublets come from octahedral $Fe^{3+}$ions. The jump up of magnetic hyperfine field of 2nd Zeeman sextet and the increasing of the values of quadrupole splitting and isomer shift of doublet below SP transition temperature could be interpreted related with the atomic displacements. The N el temperature is 715 K, the Debye temperature are 540 K for octahedral site and 380 K for tetrahedral site, respectively.