• Journal of the Korean Chemical Society
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• v.41 no.11
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• pp.590-593
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• 1997

Square-wave anodic stripping voltammetry was applied to the germanium(IV)- Morin complex in 0.5 M sulfuric acid as a supporting electrolyte. The peak potential appeared at - 0.606 V vs. Ag/AgCl. Effects of sulfuric acid concentration, Morin concentration, accumulation potential, and accumulation time on the stripping peak current for the complex of germanium(IV)-Morin were studied. Interferences by other metal cations that affect on stripping peak current were also investigated. The detection limit was found to be $3.76{\times}10^{-7}M(27 {\mu}g/L)$ for germanium(IV) using 60 seconds of accumulation time. The relative standard deviation (n=8) for 0.4 mg/L($5.5{\times}10^{-6}$ M) germanium(IV) was 3.2%.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.169-173
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• 2004

We have synthesized monodispersed $\alpha$-F $e_2$ $O_3$ nano particles to investigate the spin change during the Morin transition temperature( $T_{M}$). The particle size was founded to have a very uniform distribution of 80 nm by x-ray diffraction and size dispersion analyzer. The Mossbauer spectra between the 4.2 K and the room temperature show that $T_{M}$ was shifted and the spin states of Fe ion were changed with the particle size. The Morin transition temperature of bulk usually quoted in literature is 265 K but, it decreases with the size and no transition was found at the critical size down to 4.2K. The spin direction of 80 nm sized particles are normal to the hexagonal c-axis above the $T_{M}$ and are tilted about 28～29$^{\circ}$ below $T_{M}$, which is the [110] direction of rombohedral structure.

• Journal of the Korean Magnetics Society
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• v.1 no.1
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• pp.1-5
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• 1991

The magnetic properties of the polycrystalline ${(Fe_{2}O_{3})}_{1-x-y}{(In_{2}O_{3})}_{x}{(Eu_{2}O_{3})}_{y}$(x=0.01, y=0.02과 x=0.02, y=0.03) have been studied by the methods of X-ray diffraction, $M\"{o}ssbauer$ effect, and magnetic hysteresis measurement. The X-ray diffraction patterns show that the samples have a same crystal structure as $\alpha-Fe_{2}O_{3}$. From the analysis of the temperature dependence of the quadrupole splitting and average half-width, it is found that the Morin transition occurs in the sample of x=0.01 and y=0.02 and the spin angle defined as the angle between the [111] crystal axis and antiferromagnetic vector, changes from about $35^{\circ}$ to the (111) plane as increasing the temperature in the sample of x=0.02 and y=O.03. The temperature dependence of magnetic hyperfine field is analyzed by using the spin-wave theory. The isomer shift values at room temperature are found to be given by about 0.35mm/s for the samples which means that the Fe ions belong to $3^{+}ion$. The temperature dependence of isomer shift was analyzed by using the Debye model.