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Ni/Fe(001)의 자성과 자기이방성에 대한 제일원리계산
권오룡(Oryong Kwon),홍순철(Soon Cheol Hong) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.4
Recent theoretical calculations predicted that a system composed exclusively of 3d transition metals without 4d/5d transition metals or rare earth metals can have strong perpendicular magnetocrystalline anisotropy (MCA) if Fe and Ni layers are arranged appropriately. They considered only Fe-terminated surfaces, noting that Fe/MgO(001) and CoFeB/MgO(001) show strong perpendicular MCA. In this paper, we investigate magnetism and MCA of Ni/Fe(001) surface where Ni layer is positioned at the surface, by using complementarily the first principles calculational methods of Vienna Ab-initio Simulation Package (VASP) and Fullpotential Linearized Augmented Plane Wave (FLAPW) method. Comparing results of magnetism and MCA obtained by VASP with the results by FLAPW method, we find the VASP results do not show big difference from results by FLAPW method. Magnetic moments of Fe and Ni are enhanced due to strong hybridization between Fe and Ni bands. MCA of Ni/Fe(001) is parallel to the surface, which implies the surface termination plays a crucial role in determining MCA of a system.
B2 구조 FeX(X = Al, Si, Ni, Ga, Ge, Sn) 합금의 자기변형에 대한 제일원리계산
이선철(Sunchul Lee),Dorj Odkhuu,권오룡(Oryong Kwon),홍순철(Soon Cheol Hong) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.4
In this study we investigated magnetism and magnetostriction of B2-structured FeX (X = Al, Si, Ni, Ga, Ge, and Sn) using a firstprinciples method, in order to survey the possibility of developing a transition metal based magnetostriction material. The Fullpotential Linearized Augmented Plane Wave method was employed for solving the Kohn-Sham equation within the generalized gradient approximation for exchange-correlation interaction between electrons. FeX alloys are stabilized in ferromagnetic states except for the FeSi and FeGe alloys. Magnetostrcition coefficients of FeX (X = Al, Ni, Ga, and Sn) were calculated to be ?5, +6, ?84, ?522ppm, respectively. It is noteworthy that the magnetostriction coefficient (?522ppm) of FeSn is larger than that (+400ppm) of Gafenol.
CoFe 박막의 자성과 자기결정이방성에 대한 제일원리계산
김은구(Eun Gu Kim),제갈소영(So Young Jekal),권오룡(Oryong Kwon),홍순철(Soon Cheol Hong) 한국자기학회 2014 韓國磁氣學會誌 Vol.24 No.2
We investigate magnetism and magnetocrystalline anisotropy of CoFe thin films, using VASP code in GGA. In this study Coterminated and Fe-terminated 5-layer CoFe thin films are employed. The Co-terminated CoFe thin film shows two total energy minima at 2-dimensional lattice constants of 2.45 A and 2.76 A. The film of 2.45 A has fcc-like structure and the film of 2.76 A has bcc-like structure similarly to a bulk CoFe alloy. And the fcc-like film is more stable by the energy difference of about 160 meV compared to the bcc-like film. The Fe-terminated CoFe film shows very complicated behaviour of total energy which is suspected to be closely related to its complex magnetic structure. The Co-terminated CoFe film of 2.76 A shows perpendicular magnetocrystalline anisotropy (MCA), while the film of 2.45 does parallel MCA. The Fe-terminated CoFe film also exhibits similar MCA behaviour.