• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.175-179
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• 2015

The half-metallicity and magnetism of the (001) surfaces of $(AlP)_1/(CrP)_1$ superlattice were investigated by means of FLAPW (Full-potential Liniarized Augmented Plane Wave) method. We considered four types of (001) surface termination, i.e., Al(S)-, Cr(S)-, P(S)Al(S-1)- and P(S)Cr(S-1)-term systems. We found that only Cr(S)-term system maintains the half-metallicity at the surface as only this system has the calculated magnetic moment of integer number of bohr magnetons. The magnetic moment of Cr(S) atom in the system was $3.02{\mu}_B$ which was increased from the bulk value by the effects of band narrowing and increased spin-splitting at the surface. The electronic density of states of the P(S) atom in the P(S)Al(S-1)-term showed very sharp surface states due to the broken $p_z$ bonds at the surface. We found there is still a strong p-d hybridization between the P(S) and Cr(S-1) layers in the P(S)Cr(S-1)-term which causes a considerable increase of magnetic moment of P(S) atom.

• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.43-47
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• 2011

It is known that the Fe-Al transition metal compounds have a lot of disagreement about structural stability and magnetism. In this study, the correlation between magnetism and atomic structure of ordered $B_2$, $L1_2$, and $D0_3$ structured Fe-Al compounds has been investigated using the all-electron full-potential linearized augmented plane wave (FLAPW) method based on the generalized gradient approximation (GGA). We found that considered all the structures were calculated to be stabilized in a ferromagnetic state. The calculated spin magnetic moments of the Fe atoms for B2 and $L1_2$ structures were 0.771 and 2.373 ${\mu}_B$, respectively, and that of Fe(I) and Fe(II) in $D0_3$ structure calculated to be 2.409 ${\mu}_B$, 1.911 ${\mu}_B$, respectively. In order to investigate structural stability between $L1_2$ and $D0_3$ structures, we performed the formation enthalpy calculations. As a result, the $D0_3$ structure is found to be more favorable than $L1_2 one by energy difference 16 meV/atom, which is well consistent with the experimental observation. We understood about structural stability and magnetism for Fe-Al compounds in terms of analysis of their atomic and electronic structures.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.1-6
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• 2013

Spin-orbit coupling (SOC) effect is known to be the physical origin for various exotic magnetic phenomena in the low-dimensional systems. Recently, SOC also draws lots of attention in the study on magnetically doped thermoelectric alloys to determine their properties as the thermoelectric application as well as the topological insulator via the exact electronic structures determination near the Fermi level. In this research, aiming to investigate the spin-orbit coupling effect on the structural properties such as the lattice constants and the bulk modulus of the most widely investigated thermoelectric host material, $Bi_2Te_3$, we carried out the first-principles electronic structure calculation using the all-electron FLAPW (full-potential linearized augmented plane-wave) method. Employing both the local density approximation (LDA) and the generalized gradient approximation (GGA), the structural optimization is achieved by varying the in-plane lattice constant fixing the perpendicular lattice constant and vice versa, to find that the SOC effect increases the equilibrium lattices slightly in both directions while it markedly reduces the bulk modulus value implying the strong orientational dependence, which are attributed to the material's intrinsic structural anisotropy.

• Journal of the Korean Magnetics Society
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• v.17 no.4
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• pp.147-151
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• 2007

We have investigated the half-metallicity and magnetism for the Heusler ferromagnet $Co_2$ZrSi interfaced with semiconductor ZnTe along the (001) plane by using the full-potential linearized augmented plane wave (FLAPW) method. We considered low 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 half-metallicity 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 $Co_2$ZrSi, 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 $0.78{\mu}_B$ for the "bridge" and "antibridge" sites, respectively, which are much reduced with respect to that ($1.15{\mu}_B$) of the bulk $Co_2$ZrSi. In the case of Co/Zn, Co atoms at the "bridge" and "antibridge" sites have magnetic moments of 1.16 and $0.93{\mu}_B$, respectively, which are almost same or slightly decreased compared to that of the bulk $Co_2$ZrSi. 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 $1.13{\sim}1.30\;{\mu}_B$, which are almost same or slightly increased than that of the bulk $Co_2$ZrSi.

• Journal of Magnetics
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• v.13 no.4
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• pp.124-127
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• 2008

The magnetic and electronic properties of Ni impurity in bcc Fe ($Ni_1Fe_{26}$) are investigated using the full potential linearized augmented plane wave (FLAPW) method based the generalized gradient approximation (GGA). We found that the Ni impurity in bcc Fe increases both the lattice constant and the magnetic moment of bcc Fe. The calculated equilibrium lattice constant of $Ni_1Fe_{26}$ in the ferromagnetic state was 2.84 A, which is slightly larger than that of bcc Fe (2.83 ${\AA}$). The averaged magnetic moment per atom of $Ni_1Fe_{26}$ unit cell was calculated to be $2.24{\mu}_B$, which is greater than that of bcc Fe (2.17 ${\mu}_B$). The enhancement of magnetic moment of $Ni_1Fe_{26}$ is mainly contributed by the nearest neighbor Fe atom of Ni, i.e., Fe1, and this can be explained by the spin flip of Fe1 d states. The density of states shows that Ni impurity forms a virtual bound state (VBS), which is contributed by Ni $e_{g{\downarrow}}$ states. We suggest that the VBS caused by the Ni impurity is responsible for the spin flip of Fe1 d states.

• Journal of Magnetics
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• v.21 no.1
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• pp.6-11
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• 2016

The magnetic anisotropy energy (MAE) and the saturation magnetization $B_s$ of (110) $Fe_nCo_n$ heterostructures with n = 1, 2, and 3 are investigated in first-principles within the density functional theory by using the precise full-potential linearized augmented plane wave (FLAPW) method. We compare the results employing two different exchange correlation potentials, that is, the local density approximation (LDA) and the generalized gradient approximation (GGA), and include the spin-orbit coupling interaction of the valence states in the second variational way. The MAE is found to be enhanced significantly compared to those of bulk Fe and Co and the magnetic easy axis is in-plane in agreement with experiment. Also the MAE exhibits the in-plane angle dependence with a two-fold anisotropy showing that the $[1{\overline{I}}0]$ direction is the most favored spin direction. We found that as the periodicity increases, (i) the saturation magnetization $B_s$ decreases due to the reduced magnetic moment of Fe far from the interface, (ii) the strength of in-plane preference of spin direction increases yielding enhancement of MAE, and (iii) the volume anisotropy coefficient decreases because the volume increase outdo the MAE enhancement.

• Journal of Magnetics
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• v.6 no.3
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• pp.80-82
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• 2001

We have investigated magnetism of $Fe_2 /Ir_4$(001) superlattice in terms of a first-principles calculation by using an all-electron full-potential linearized augmented plane-wave (FLAPW) method within the generalized gradient approximation (GGA). We considered two magnetic states, the ferromagnetic (FM) and antiferromagnetic (AFM) coupled states between the Fe layers. It was found that the FM state was energetically more stable than the AFM one by 0.166 eV. Calculated magnetic moments of the Fe layers were, in absolute values, 2.45$\mu_B$ and 2.30 $\mu_B$for the FM and AFM states, respectively. We also found that the Ir layers had very small magnetic moments less than 0.1 $\mu_B$ for both magnetic states. In all the magnetic states, the subinterface Ir layers were coupled antiferromagnetically to the interface Ir layers, while the interface Ir layers were always coupled frerromagnetically to the interface Fe layers. These results contradicted to recent experimental reports of magnetically "dead"Fe layers in Fe/Ir superlattices for which the Fe layer thickness was less than two atomic layers. We attributed that the experimentally observed "dead"Fe layers were due to possible interdiffusion between Ir and Fe layers.en Ir and Fe layers.

• Journal of Magnetics
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• v.7 no.4
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• pp.132-137
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• 2002

The electronic structures and magnetism of the non-oxide perovskite MgCFe$_3$(001) surface were investigated by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA). We considered both of the MgFe terminated (MgFe-Term) and the CFe terminated (CFe-Term) surfaces. We found that the minority spin d-bands of Fe(S) of the MgFe-Term are strongly localized and Fermi level (EF) lies just below the sharp peak of the minority spin d-band of Fe(S), while the minority spin d-bands of Fe(S) of the CFe-Term are not localized much and Fermi level (E$_F$) lies in the middle of two peaks of the minority spins. The majority Fe(S) d-band width of MgFe- Term is narrower than that of the CFe-Term. It is found that the magnetic moment of Fe(S) of the MgFe- Term is 2.51 ${\mu}$$_B$, which is much larger than that of 1.97 ${\mu}$$_B$ of the CFe-Term.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.131-135
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• 1999

The electronic structures and properties of layered perovskite $LaSrMnO_4$ and $SR^2MnO_4$ have been determined using the local-density full potential Imearized augmented plane wave method. The total energy calculations show that the antiterromagnetic state has lower energy than the ferromagnetic state in $LaSrMnO_4$. The jahn-Teller distortion of Mn-O octahedron produces the energy gap and the $3z^2-r^2$ orbital ordering, which stabilizes 2 dimensional antiferromagnetis state.

• Journal of the Korean Magnetics Society
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• v.23 no.4
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• pp.117-121
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• 2013

In this study we investigated magnetism and magnetostriction of B2-structured FeX (X = Al, Si, Ni, Ga, Ge, and Sn) using a first-principles method, in order to survey the possibility of developing a transition metal based magnetostriction material. The Full-potential 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.