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Local structures of equiatomic CoTi alloy films with various degrees of structural order
이영백,황정남,J. Y. Rhee,Y. Jeon,Y.V. Kudryavtsev,Y.V. Kudryavtsev 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.2
The microstructures of ordered B2-phase and amorphous-like equiatomic CoTi alloy lms have been investigated by using X-ray absorption spectroscopy. Analysis of the extended X-ray absorption ne structure (EXAFS) data elucidates, at least in a local sense, that both Co and Ti atoms are arranged in an ordered cubic-B2 structure for the lm deposited on a heated substrate (730 K) while the lm deposited on a the substrate cooled down to 150 K is amorphous-like. The lm deposited at 150 K has the same main peak position as the pure Co lm in the Co K-edge Fourier transform EXAFS spectrum. This indicates that the radial distance is the same as for a pure Co film, and re ects the formation of Co clusters, which is attributed to an increase in the number of nearest Co-Co bondings and implies the formation of a considerable amount of antistructure Co atoms (Co atoms at Ti sites) and nearest-neighbor clustering of Co atoms. These results are consistent with recent observations and interpretation of a weakly ferromagnetic behavior in CoTi lms deposited at 150 K [Y. P. Lee et al, Phys. Rev. B 60, 8067 (1999)] and their other peculiar physical properties.
Structural and Magnetic Properties, and Electronic Structures of Fe-Mn-Ga Alloys
Y. V. Kudryavtsev,N. V. Uvarov,V. N. Iermolenko,J. Dubowik,J. Y Rhee,유영준,이영백 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10
We report the structural and the magnetic investigations on bulk Fe-Mn-Ga alloy and the films with a stoichiometry of 1:1:1. Both the alloy and the films reveal an unstable crystallographic structure. While the bulk alloy appears to possess a mixed ferromagnetic hexagonal structure with the presence of a (Mn/Fe)9Ga5 ζ-phase, the films have ferromagnetic cubic phases in various types of structural ordering that depend on the deposition and the annealing conditions. Exchange bias and enhanced coercivity occur simultaneously in B2-type ordered FeMnGa films, revealing an exchange coupling between coexisting antiferromagnetic and ferromagnetic phases. The experimental results are compared with the results of the first-principle calculations.
Y. P. Lee,S. M. Kim,Y. V. Kudryavtsev,Y. N. Makogon 한국진공학회(ASCT) 2003 Applied Science and Convergence Technology Vol.12 No.S1
Solid-state reactions in Ni/Si multilayered films (MLF) with an overall stoichiometry of Ni₂Si, NiSi and NiSi₂, induced by ion-beam mixing (IBM) and thermal annealing, were studied by using spectroscopic ellipsometry and magnetooptical spectroscopy as well as x-ray diffraction (XRD). The mixing was performed with Ar^+ ions of an energy of 80 keV and a dose of 1.5×10^(16) Ar^+/㎠. It was shown that the IBM induces structural changes in the Ni/Si MLF, which cannot be detected by XRD but are confidently recognized by the optical method. A thermal annealing at 673 K of the Ni/Si MLF with an overall stoichiometry of NiSi and NiSi₂ causes formation of the first η-NiSi phase. The first trace for NiSi₂ phase on the background of NiSi one was detected by XRD after an annealing at 1073 K while, according to the optical results, NiSi₂ turns out be the dominant phase for the annealed Ni/Si MLF with an overall stoichiometry of NiSi₂.