http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Energy Product and Coercivity of a Rare-earth-free Multilayer FeCo/FePt Exchange Spring Magnet
김동유,Arqum Hashmi,홍지상 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.6
Using the full potential linearized augmented plane wave (FLAPW) method, we have explored the energy product and the coercivity field of rare-earth-free FeCo/FePt(001) multilayered exchange spring magnet systems. We have considered 5 and 7 monolayers (ML) of a FePt hard layer and 3, 5, 7, and 9 ML of a FeCo soft layer. The FeCo soft layers are found to show close to half metallic features, while the FePt hard layers manifest conventional metallic behavior. A giant perpendicular magnetocrystalline anisotropy energy (EMCA) is observed. For instance, an EMCA of 27.24 meV/cell is found in FeCo(9 ML)/FePt(7 ML) multilayer structure. The energy product almost linearly increases with increasing FeCo thickness, while the coercivity filed shows the opposite behavior. Interestingly, we have obtained that the multilayer structures display very large energy product and coercivity field. For example, FeCo(9 ML)/FePt(5 ML) multilayer has an energy product of about 82 MGOe and a coercivity field of about 130 KOe. Moreover, we find that the multilayer system may show enhanced coercivity field compared with that found in FeCo/FePt bilayer film structures, while the energy product is comparable to that observed in bilayer films. Therefore, our results may imply that the FeCo/FePt multilayer can be employed as a potential rare- earth-free permanent magnet material.
Magnetic Property of a One-dimensional FePt Atomic Chain on a NiAl(110) Surface
김동유,홍지상 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.11
Through the full potential linearized augmented plane wave (FLAPW) method, the magnetic property of a one-dimensional (1D) FePt diatomic chain has been explored. We find a ferromagnetic (FM) ground state for both free-standing and supported systems on a NiAl(110) surface. In the free-standing state, Fe and Pt atoms have magnetic moments of 3.47 and 0.74 <i>μ<sub>B</sub></i>, respectively. On a NiAl(110) surface, the magnetic moment of Fe becomes 2.95 <i>μ<sub>B</sub></i>, and there is no spin polarization in the Pt atom. In contrast, the surface Ni has an induced magnetic moment of 0.2 <i>μ<sub>B</sub></i>. The direction of magnetization and the strength of magnetic anisotropy energy are found to be substantially affected by the NiAl(110) surface. For instance, the magnetization aligns perpendicular to the chain axis for the free-standing state, and the calculated magnetic anisotropy energy is 18.33 meV/cell, however the magnetization direction of a supported system aligns parallel to the chain axis with an anisotropy energy of 0.568 meV/cell. Overall, we find that the magnetic anisotropy of a 1D FePt atomic chain is substantially influenced by the presence of the NiAl(110) substrate.
Magnetic Properties of MgN and MgC Films on MgO(001) Surfaces
김동유,홍지상 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.3
Using the full potential linearized augmented plane wave (FLAPW) method, we have explored the magnetic properties of one monolayer (ML) of MgN and MgC films on MgO(001) surfaces. In addition,the influence of a MgO capping layer on the magnetic states of MgC and MgN films has been investigated. We observed that both MgC/MgO(001) and MgN/MgO(001) display ferromagnetic (FM) state. Interestingly, we find that both free standing MgN film and MgN/MgO(001) systems display half metallic feature. The calculated magnetic moments of C and N in MgC/MgO(001)and MgN/MgO(001) are 0.3 μB and 0.57 μB, respectively. The essential magnetic properties of both systems are unchanged even in the presence of a MgO capping layer. In particular, the half metallic feature in MgN/MgO(001) is still maintained in both the MgN/MgO(001) and the MgO(1 ML)/MgN/MgO(001) systems. The adsorption energy calculations indicate that the MgC layer is physisorbed on MgO(001), while the MgN layer is chemisorbed. Due to the rigid half metallic feature and the character of adsorption, the MgN/MgO(001) can be utilized for potential spintronics purposes.