• Journal of Magnetics
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• v.13 no.4
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• pp.115-119
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• 2008

The authors predicted that $Co_2HfSi$, a $Co_2$-based full Heusler alloy, is being a half-metallic ferromagnet by first-principles calculations using the all electron full-potential linearized augmented plane wave method which adopts the generalized gradient approximation. The integer value of the calculated total magnetic moment of 2.00 ${\mu}_B$ per formula unit and a spin gap of 0.69 eV in spin down state confirmed the half-metallicity of bulk $Co_2HfSi$. For the $Co_2HfSi$(001) surface, we considered two possible surface terminations, namely, Co terminated and HfSi terminated surfaces. It was found that half-metallicity was retained at the HfSi-terminated surface but not at the Co-terminated surface. The magnetic moment of surface Co atoms in the Co-terminated surface was slightly lower than that of Co atoms in deep inner-layers, whereas the magnetic moments of Hf and Si atoms at the HfSi-terminated surface were almost same as those in deep inner-layers.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1370-1376
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• 2018

The electronic structures, magnetic properties and half-metallicity in $Zr_2RuZ$ (Z = Ga, In, Tl, Ge, Sn, and Pb) alloys with $AlCu_2Mn-$ and $CuHg_2Ti$-type structures were investigated using first-principles density functional theory (DFT) calculations. The calculations showed that $Zr_2RuIn$, $Zr_2RuTl$, $Zr_2RuSn$, and $Zr_2RuPb$ compounds with $CuHg_2Ti$-type structures were half-metallic ferromagnets with half-metallic band gaps of 0.18, 0.24, 0.22, and 0.27 eV, respectively. The half-metallicity originated from d-d and covalent hybridizations between the transition metals Zr and Ru. The total magnetic moments of the $Zr_2RuZ$ (Z = In, Tl, Sn, and Pb) compounds with $CuHg_2Ti$-type structures were integer values of $1{\mu}B$ and $2{\mu}B$, which is in agreement with Slater-Pauling rule ($M_{tot}=Z_{tot}-18$). Among these compounds, $Zr_2RuIn$ and $Zr_2RuTl$ were half-metals over relatively wide regions of the lattice constants, indicating that these two new Heusler alloys are ideal candidates for use in spintronic devices.

• Journal of the Korean Magnetics Society
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• v.18 no.4
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• pp.131-135
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• 2008

The electronic structures, magnetism, and half-metallicity of the full-Heusler $Co_2TiSn$(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 ${\mu}_B$ 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 ${\mu}_B$).

• Journal of the Korean Magnetics Society
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• v.23 no.6
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• pp.179-183
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• 2013

The half-metallicity and magnetism for compounds of the $N_{(2-0.5n)}O_{0.5}nKCa$ (n = 0~4), which was based on the $d^0$ Heusler half-metals of $N_2KCa$ and $O_2KCa$, were investigated by means of first-principles band calculation method. From the calculated total magnetic moments and the density of states, we found that these three compounds have the half-metallicity. The magnetic moments of the N and O atoms in these compounds were considerably increased compared to those of pure $N_2KCa$ and $O_2KCa$. The K atoms have a large negative magnetic moments. The relationship between the value of magnetic moments for each atom and density of states are discussed.

• Journal of Magnetics
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• v.18 no.4
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• pp.375-379
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• 2013

The electronic and the magnetic properties of (001) surface of $KCaN_2$ half-metallic compound with full-Heusler structure are studied with the use of a full-potential linearized augmented plane wave method. Two possible terminations of the surface are considered and only the one with N atoms in the topmost layer is found to retain the half-metallic properties of the bulk. The magnetic properties of N-terminated surface are enhanced compared with the properties of the bulk. The calculated magnetic moments on the N atoms in the $KCaN_2$ are 1.26 ${\mu}_B$ in the bulk and 1.90 ${\mu}_B$ at the surface. The subsurface metal atoms are also slightly polarized. In the surface terminated with metal atoms, not only the half-metallicity is destroyed, but also the magnetic properties of the system are weakened.

• Journal of the Korean Magnetics Society
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• v.15 no.5
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• pp.257-260
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• 2005

We investigated the half-metallicity and magnetism for the zinc-blende CrS(001) surfaces by use of the full-potential linearized augmented plane wave (FLAPW) method. We considered two-types of (001) surfaces terminated by Cr (Cr-Term) and S (S-Term) atoms, respectively. From the calculated layer-by-layer density of states, it is found that both of the systems retain the half-metallicity at the (001) surfaces. The calculated magnetic moment ($4.07\;{\mu}_B$) for the CrS(S) atom in Cr-Term is enhanced considerably compared to the bulk value ($3.61\;{\mu}_B$) while that ($3.15\;{\mu}_B$) of the Cr(S-1) in S-Term is much reduced.

• Journal of Magnetics
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• v.21 no.1
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• pp.1-5
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• 2016

We investigated the half-metallicity and magnetism at the (001) and (110) surfaces of CsSe in cesium chloride and zinc-blende structures by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. From the calculated local density of states, we found that all the surfaces preserve the half-metallicity of the bulk structures. The surfaces with a greater polarity have stronger ferromagnetic properties when terminated with Se atoms; the non-polar surfaces do not change their electronic or magnetic properties considerably as compared with the bulk structures.

• Journal of Magnetics
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• v.20 no.1
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• pp.1-7
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• 2015

We investigated the half-metallicity and magnetism at the (001) and (110) surfaces of YC in zinc-blende structure by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. From the calculated local density of states, we found that neither (001) nor (110) surface preserves the half-metallicity. While the magnetic moment of Y atom in the YC bulk is $0.116{\mu}_B$, it is $0.057{\mu}_B$ at the topmost layer of Y-terminated (001) surface. On the contrary, C-terminated (001) YC surface exhibits stronger magnetism than the bulk structure; the calculated magnetic moment on topmost C atom is $1.084{\mu}_B$, while that of C atom in the bulk structure is $0.423{\mu}_B$. The magnetic properties of the non-polar (110) YC surface are slightly enhanced as compared with the bulk structure.

• Journal of the Korean Magnetics Society
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• v.25 no.2
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• pp.31-38
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• 2015

Recently, a first-principles study led to a prediction that quaternary Heusler compounds, CoFeCrZ (Z = Ga, Ge) are excellent half-metallic ferromagnets. In this study, we investigate the electronic and the magnetic properties at the (001) surfaces of CoFeCrGa and CoFeCrGe by means of the full-potential linearized augmented plane wave (FLAPW) method within generalized gradient approximation. We considered two types of surface termination: CoFe-terminated and CrZ-terminated surfaces, Z being either Ga or Ge. From the calculated total magnetic moments and the local density of states, we found that half-metallicity is not preserved for all the surfaces. But the calculated atomic density of states showed that CrGa-terminated surface of the CoFeCrGa is almost half-metallic. The magnetic moment of the Co, Fe, or Cr atoms at the surface or subsurface layers in each system had very different values.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.121-121
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• 2011