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W(110)위에 성장한 Fe 웃층의 전자 및 자기적 성질
홍순철(Soon C. Hong),이재일(Jae Il Lee),A. J. Freeman(A. J. Freeman) 한국자기학회 1991 韓國磁氣學會誌 Vol.1 No.2
The electronic and magnetic structure of Fe overlayers on W(110) is determined by means of the all-electron local spin density full potential linearized augmented plane wave (FLAPW) method with a single slab approach. Charge and spin densities, magnetic moments, contact hyperfine fields, and layer projected density of states (LDOS) are presented. For bilayer Fe coverage, we find magnetic moments to be 2.90 and 2.30 μ_B for the surface and subsurface Fe layers, respectively, corresponding to a 18% enhancement of the total magnetization compared with the calculated bulk value (2.22μ_B);For monolayer coverage the moment is 2.56μ_B which is enhanced by 16% compared to bulk. Unusual changes in the magnetic hyperfine interaction are found in going from a monolayer to a bilayer coverage. Comparison of the results to the theoretical ones of the clean Fe(110) to discuss the hybridization and the negative pressure effects. We discuss our results by comparing them to experimental results.
덩치 망간의 결정 구조와 자성 간의 상호관계에 관한 제일원리계산
노태환(T. H. Rho),홍순철(Soon C. Hong) 한국자기학회 2002 韓國磁氣學會誌 Vol.12 No.3
Manganese is known to have a very complicated crystal structure due to its complex magnetism. In this study we investigated the magnetism of fcc and bcc Mn as functions of lattice constants, using Full-potential Linearized Augmented Plane Wave (FLAPW) and assuming para-, ferro-, and antiferro-magnetic states. The antiferromagnetic and ferromagnetic states were calculated to be energetically stable for fcc Mn and bcc Mn, respectively. The lattice constants of fcc and bcc Mn at equilibrium are 6.750 and 5.314 a.u. and the magnetic moments are 1.15 and 0.85 μ_B, respectively. The ferro- and antiferro-magnetic states are so unstable (not even metastable) that the states were converged to the other magnetic states in self-consistent calculations.
이재일(Jae Il Lee),조이현(Li-Hyun Cho),홍순철(Soon C. Hong) 한국자기학회 1993 韓國磁氣學會誌 Vol.3 No.3
The structural and electronic properties of the Li monolayer have been studied using the total energy FLAPW(Full-Potential Linearized Augmented Plane Wave) band method. It is found that the triangular lattice is more stable than the square lattice from the result of total energy calculation by varying the Wigner-Seitz radius, r_s. The equilibrium Wigner-Seitz radius r_s for the triangular lattice is calculated to be 3.7 a.u. From the spin polarized calculation it is also found that the metallic ferromagnetic transition and the full spin polarization occur at r_s=4.2 u. and at r_s=5.3 a.u., respectively.
전이금속이 도핑된 ZnO의 전자구조와 자성에 대한 제일원리계산
윤선영(Sun Young Yun),차기범(Gi-Beom Cha),Sunglae Cho(Sunglae Cho),홍순철(Soon C. Hong) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.1
In this study we investigate the electronic structure and magnetism of transition metal (TM=Ti, Cr, Mn, Fe, Co, Ni, Ru, Pd, Ag) doped ZnO(TM_(0.25)Zn_(0.75)O), which are expected to have high Curie temperature. Full-potential Linearized Augmented Plane Wave (FLAPW) method is adopted with exchange-correlation potential expressed as general gradient approximation (GGA). The calculated magnetic moments of (TM_(0.25)Zn_(0.75)O) are 0.83, 3.03, 4.03, 3.48, 2.47, 1.56, 0.43, 0.75, 0.01 μ_B for TM=Ti, Cr, Mn, Fe, Co, Ni, Ru, Pd, Ag, respectively. The nearest neighbor O atom to the transition metal is calculated to have a significant magnetic moment of about 0.1 μ_B, due to strong hybridization between O-p and TM-d bands. As the results, the systems may have larger magnetic moments in total, compared to the corresponding isolated atoms. The 3d TM doped systems exhibit the half-metallic character except Co, whereas the 4d TM doped systems behave like normal metals and low spin polarization at the Fermi levels.
제일원리계산방법에 의한 결정 구조에 따른 덩치 망간의 전자 구조와 자성 변화 연구 : 면심입방과체심입방 구조의 망간 fcc and bcc Mn
노태환,홍순철 울산대학교 2002 자연과학논문집 Vol.11 No.2
덩치 망간의 평형상태에서의 결정구조와 자성 구조는 아주 복잡한 것으로 알려져 있다. 본 연구에서는 자성 연구에서 가장 적합한 방법으로 알려져 있는 Full-potential Linearized Augmented Plane Wave(FLAPW) 방법을 사용하여 격자상수의 함수로 면심입방 Mn과 체심입방 Mn의 계산 가능한 자성 상태(상자성, 강자성, 반강자성 상태)의 총에너지를 계산하여 결정구조에 따른 Mn의 자성 변화를 연구하였다. 계산 결과, 면심입방 Mn은 반강자성 상태가 안정하고 체심입방 Mn은 강자성상태가 안정한 것으로 밝혀졌다. 면심입방 Mn과 체심입방 Mn의 평형상태의 격자상수는 각각 6.750, 5.314 a.u. 이었고 자기모멘트는 1.15 μ_B과 0.85 μ_B인 것으로 계산되었다. 면심입방의 경우는 강자성 상태가, 체심입방의 경우는 반강자성 상태가 전혀 안정되지 못하는 것으로 나타났다. Manganese is known to have a very complicated crystal structure due to its complex magnetism. In this study we investigated the magnetism of fee and bcc Mn as functions of lattice constants, using Full-potential Linearized Augmented Plane Wave(FLAPW) method and assuming para-, ferro-, and antifcrro-magnetic states. The anti ferromagnetic and ferromagnetic states were calculated to be energetically stable for fee Mn and bcc Mn, respectively. The lattice constants of fee and bcc Mn at equilibrium are 6.750 and 5.314 a.u. and the magnetic moments are 1.15 and 0.85 μ_B, respectively. The ferro- and antiferro-magnetic states are so unstable (not even metastable) that the states were converged to the other magnetic states in self-consistent calculations.