• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.51-56
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• 2012

In the present study, we investigated the effect of mechanical alloying (MA) on the formation of amorphous VCo system through solid state reaction during ball milling. Two types of powder samples, ${\sigma}$-VCo intermetallic compound and $V_{50}Co_{50}$ powder mixture, were applied as a starting materials. With increasing milling time, a structural characteristics into the amorphous state is distinctly observed from the structural factor and radial distribution by X-ray diffraction. Amorphization has been observed in all two types of samples after the milling for 120 hrs. DSC spectrum of $V_{50}Co_{50}$ powder sample milled for 60 hrs indicates a sharp exothermic peak from the crystallization at $600^{\circ}C$. The structure factor, S(Q) and radial distribution function, RDF(r), observed by X-ray diffraction gradually change into a structure characteristic of an amorphous state with increasing MA time.

• Journal of the Korean Magnetics Society
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• v.3 no.3
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• pp.179-184
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• 1993

The X-ray diffraction pattern of amorphous $Fe_{78}Si_{9}B_{13}$ alloy was analyzed to obtain the radial distribution function (RDF) where the first peak was in the form of Gaussian function. The calculated coordination number of the form of Gaussian functiono The calculated coordination number of the sample is 13.5, the mean distance betweeon near-neighbor atoms $r_{0}$ is $2.595{\AA}$ and a Gaussian parametet ${\delta}r$ indicating near-neighbor atomic distri-bution is $0.27{\AA}$. The temperature dependence of saturated magnetization at low temperature could be explained by spin wave excitations theory yielding the spin wave stiffness constant as $117.8\;meV\;{\AA}^2$. Also, we tried to fit the observed temperature dependence of saturated magnetization with the Handrich's equation of the modified molecular field theory for the amorphous ferromagnet. Nice fittings are obtained when we used the parameters ${\Delta}=0.32$(S=1/2) and ${\Delta}=0.23$(S=1), respectively. Finally, the calculated spin wave stiffness constant using the parameters and the structural data are $149\;meV\;{\AA}^2$ for S=1/2 and $138\;meV\;{\AA}^2$ for S=1, respectively. The mean exchange coupling integral between near-neighbor atoms was estimated to be 17.9 meV for S=1/2 and 6.7 meV for S=1.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.4
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• pp.129-134
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• 2004

In this study, we investigated the effect of a nitrogen atom on the amorphization of V-Fe alloy through solid-gas reaction during mechanical alloying (MA). MA by planetary ball mill of $V_{70}Fe_{30}$ elemental powders was carried out under the nitrogen gas atmosphere. Amorphization has been observed after 160 hours of ball milling in this case. The DSC spectrum for the mechanically alloyed ($V_{70}Fe$_{30}$)_{0.89}N_{0.11}$ powders exhibits a sharp exothermic peak due to crystallization at about $600^{\circ}C$. Structural transformation from the bcc crystalline to amorphous states was also observed through X-ray and neutron diffractions. We take a full advantage of a negligibly small scattering length of the V atom in the neutron diffraction measurement. During amorphization process the octahedral unit, which is typical of a polyhedron formed in any crystal structures, was preferentially destroyed and transformed into the tetrahedral unit. Futhermore, neutron diffraction measurements revealed that a nitrogen atom is selectively situated at a center of the polyhedron formed by V atoms.