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(CrAs)₃(MnAs)₃(110) 초격자의 전자구조와 자성에 대한 제일원리 연구
이재일(J. I. Lee),홍순철(S. C. Hong) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.2
We investigated the magnetism and electronic structures for the layered structures consisting of (110) layers of zinc-blende CrAs and MnAs. We calculated the electronic structures for (CrAs)₃(MnAs)₃(110) superlattice consisted of alternating three layers of CrAs(110) and MnAs(110) by the full-potential linearized augmented plane wave (FLAPW) method. The calculated magnetic moment of Cr in interface layer (3.07 μ<SUB>B</SUB>) was slightly larger than that of Cr atom in center layer (3.06 μ<SUB>B</SUB>), while that of interface Mn atom (3.74 μ<SUB>B</SUB>) was slightly smaller than the value of Mn atom in center layer (3.76 μ<SUB>B</SUB>). The electronic structure and half-metallicity in this superlattice were discussed using the calculated density of states.
Ag(001) 표면 위에 놀인 Fe 선의 자성과 전자구조
김영구(Y. J. Jin),이재일(J. I. Lee) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.4
The electronic structure and magnetism of Fe chain along the [110] direction on Ag(001) were investigated by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within generalized gradient approximation (GGA). The magnetic moment of Fe atom in Fe chain is calculated to be 3.02 μ_B, which is slightly larger than that (2.99 μ_B) of the Fe[110] chain on Cu(001). The reduced coordination number for the Fe chain induced the Fe-d band narrowing and exchange-splitting enhancement, which are responsible for the large magnetic moment of the Fe chain. The calculated band width of the Fe-d band and the exchangesplitting are 1.7 eV and 3.2 eV, respectively.
Co₂ZrSi/ZnTe(001)계면의 자성과 반쪽금속성에 대한 제일원리 연구
김영구(Y. J. Jin),이재일(J. I. Lee) 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.4
We have investigated the half-metallicity and magnetism for the Heusler ferromagnet Co₂ZrSi interfaced with semiconductor ZnTe along the (001) plane by using the full-potential linearized augmented plane wave (FLAPW) method. We considered four types of possible interfaces: ZrSi/Zn, ZrSi/Te, Co/Zn, and Co/Te, respectively. From the calculated density of states, it was found that the halfmetallicity was lost at all the interfaces, however for the Co/Te system the value of minority spin density of states was close to zero at the Fermi level. These facts are due to the interface states, appeared in the minority spin gap in bulk Co₂ZrSi, caused by the changes of the coordination and symmetry and the hybridizations between the interface atoms. At the Co/Te interface, the magnetic moments of Co atoms are 0.68 and 0.78 μ<SUB>B</SUB> for the “bridge” and “antibridge” sites, respectively, which are much reduced with respect to that (1.15 μ<SUB>B</SUB>) of the bulk Co₂ZrSi. In the case of Co/Zn, Co atoms at the “bridge” and “antibridge” sites have magnetic moments of 1.16 and 0.93 μ<SUB>B</SUB>, respectively, which are almost same or slightly decreased compared to that of the bulk Co₂ZrSi. On the other hand, for the ZrSi/Zn and ZrSi/Te systems, the magnetic moments of Co atoms at the sub-interface layers are in the range of 1.13~1.30 μ<SUB>B</SUB>, which are almost same or slightly increased than that of the bulk Co₂ZrSi.
장영록,송기명,이재일,Jang, Y.R.,Song, Ki-Myung,Lee, J.I. 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.3
CsCl 구조를 가진 VRu(001) 표면의 자기적 성질을 일반기울기근사(GGA)를 채택한 총퍼텐셜선형보강평면파(FLAPW) 에너지 띠 계산 방법을 이용하여 이론적으로 연구하였다. 이를 위해 각기 V 및 Ru 원자층으로 끝나는 두 개의 (001) 표면을 고려하였다. 계산된 머핀-틴 구 내의 다수 및 소수 전자의 수로부터 V로 끝나는 표면의 자기모멘트는 $1.71_{{\mu}_B}$로 매우 큰 값을 가졌으며, Ru로 끝나는 표면은 자성이 거의 없는 것으로 계산되었다. 이러한 자성을 계산된 스핀분극상태밀도와 스핀전하밀도와 연관지어 설명하였다. We investigated the magnetic properties of VRu(001) surface by using the all electron full-potenial linearized augmented planewave (FLAPW) energy band method within the GGA. We consider two different configurations, V and Ru surface layers, respectively. The V atoms in surface layer was calculated to have large magnetic moment of $1.71_{{\mu}_B}$ while the Ru surface layer to have nearly nonmagnetic state. The calculated spin-polarized density of states. spin density contour, and charge density were discussed in relation to the magnetic properties of VRu(001) surface.
Co₂TiSn(001) 표면의 자성 및 반쪽금속성에 대한 제일원리연구
김영구(Y. J. Jin),이재일(J. I. Lee) 한국자기학회 2008 韓國磁氣學會誌 Vol.18 No.4
The electronic structures, magnetism, and half-metallicity of the full-Heusler Co₂TiSn (001) surfaces have been investigated by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. We have considered both of the Co atoms terminated (Co-term) and the TiSn atoms terminated (TiSn-term) surfaces. From the calculated density of states, we found that the half-metallicity was destroyed at the surface of the Co-term, while the half-metallicity was retained at the TiSn-term. For the surface of the Co-term, due to the reduced coordination number the occupied minority d-states were shifted to high energy regions and that cross the Fermi level, thus destroy the surface half-metallicity. On the other hand the surface states at the surface of the TiSn-term were located just below the Fermi level, which reduces the minority spin-gap with respect to that of the center layer. The calculated magnetic moment of the surface Co atom for the Co-term was increased by 10 % to 1.16 μB with respect to that of the inner-layers, while the magnetic moment of the subsurface Co atom in the TiSn-term has almost same value of the innerlayers (1.03 μB).
나노 구조 철띠의 자성과 전자구조에 대한 제일원리 연구
변영신(Y. Byun),이재일(J. I. Lee) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.5
We investigated the magnetic properties of Fe nanostripes by using the all electron full-potenial linearized augmented plane-wave (FLAPW) energy band method within the generalized gradient approximation (GGA). The magnetic moments of the Fe atoms in the edge Fe chains of the stripes composed of three, five, and seven chains have saturated values of 2.97 or 2.98 μ<SUB>B</SUB>, and the values of the center chains are 2.82 μ<SUB>B</SUB> which is similar to that of 2D square lattice. The charge and spin density contour plots showed that the flat distribution in the edge region of the stripes, and it is due to the spilled out p-electrons from the atoms in the edge line. The calculated density of states for the edge atoms in the stripes with seven Fe chains showed that the narrowed width compared to that of center atoms due to the band narrowing effect at the edge.