• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.127.1-127.1
• /
• 2013

Recent experimental evidence that fluorinated graphene creates local magnetic moments around F adatoms has not been supported by semilocal density-functional theory (DFT) calculations where the adsorption of an F adatom induces no magnetic moment in graphene. Here, we show that such an incorrect prediction of the nonmagnetic ground state is due to the self-interaction error inherent in semilocal exchange-correlation functionals. The present hybrid DFT calculation for an F adatom on graphene predicts not only a spin-polarized ground state with a spin moment of ${\sim}1{\mu}_B$, but also a long-range spin polarization caused by the bipartite nature of the graphene lattice as well as the induced spin polarization of the graphene states. The results provide support for the experimental observations of local magnetic moments in fluorinated graphene.

• 반도체디스플레이기술학회지
• /
• 제9권3호
• /
• pp.1-4
• /
• 2010

First-principles calculations based on spin density functional theory are performed to study the spin-resolved electronic properties of AlN doped with a Cu concentration of 6.25%-18.75%. The ferromagnetic state is more energetically favorable state than the antiferromagnetic state or the nonmagnetic state. For $Al_{0.9375}Cu_{0.0625}N$, a global magnetic moment of 1.26 mB per supercell, with a localized magnetic moment of 0.75 $m_B$ per Cu atom is found. The magnetic moment is reduced due to an increase in the number of Cu atoms occupying adjacent cation lattice position. For $Al_{0.8125}Cu_{0.1875}N$, the magnetism of the supercell disappears by the interaction of the neighboring Cu atoms. The nonmagnetic to ferromagnetic phase transition is found to occur at this Cu concentration. The range of concentrations that are spin-polarized should be restricted within very narrow.

• Current Applied Physics
• /
• 제18권11호
• /
• pp.1182-1184
• /
• 2018

The combination of angular spin momentum with electronics is a promising successor to charge-based electronics. The conduction bands in GaAs may become spin-polarized via optical spin pumping, doping with magnetic ions, or induction of a moment with an external magnetic field. We investigated the spin populations in GaAs with x-ray magnetic circular dichroism for each of these three cases. We find strong anti-symmetric lineshapes at the Ga $L_3$ edge indicating conduction band spin splitting, with differences in line width and amplitude depending on the source of spin polarization.

• 한국자기학회지
• /
• 제20권5호
• /
• pp.201-205
• /
• 2010

X-선 자기 원형 이색성 측정은 자성물질을 구성하는 원소별 자기적 성질의 측정 및 궤도 자기 모멘트와 스핀 자기 모멘트를 구별하여 측정할 수 있다는 장점으로 인해 여러 가지 자성 신물질 및 다양한 기능성 자성 다층 박막의 연구에 많이 이용되어 왔다. 이 글에서는 이러한 X-선 자기 원형 이색성 현상의 원리 및 실험 방법 등을 설명하겠다. 또한 몇 가지 X-선 자기 원형 이색성을 이용한 최근 몇 가지 연구도 소개하려 한다.

• 한국진공학회지
• /
• 제6권S1호
• /
• pp.53-58
• /
• 1997

It is well known that the equiatomic FeAl alloy crystallizes in a paramagnetic CsCl structure and is very stable in a wide temperature range owing to a significant charge transfer from Al to Fe. A presence of structural defects normally enhances the magnetic and magneto-optical properties of this alloy. In this study spin-resolved photoemission and magnetic circular dichroism (MCD) were carried out on both ordered and disordered $Fe_{0.52}Al_{0.48}$ alloy films. The disordered state in the alloy films was obtained by a vapor quenching deposition on cooled substrates. It is shown that the order-disorder transition in the Fe0.52Al0.48 alloy films leads to a significant change in the spin polarization. Form the MCD results the orbital and spin magnetic moments of the constituent atoms are obtained. According to the sum rule the spin and orbital magnetic moments of Fe in the disordered FeAl film are $\mu\frac{SR}{spin}=0.8\mu_B$ and $\mu\frac{SR}{orb}=0.14\mu_B$ respectively. The spin magnetic moment is also evaluated to be $\mu\frac{BR}{spin}=0.77\mu_B$ by the branching ration method employing a photon polarization of 90%.

• 한국초전도ㆍ저온공학회논문지
• /
• 제19권3호
• /
• pp.23-26
• /
• 2017

We have studied magnetic and transport properties of NbN/FeN/Cu/FeN/FeMn spin-valve structure. In-plane magnetic moment exhibited typical hysteresis loops of spin valves in the normal state of NbN film at 20 K. On the other hand, the magnetic hysteresis loop in the superconducting state exhibited more complex behavior in which exchange bias provided by antiferrmagnetic FeMn layer to adjacent FeN layer was disturbed by superconductivity. Because of this, the ideal superconducting spin-valve effect was not detected. Instead the stray field originated from unsaturated magnetic states dominated the transport properties of NbN/FeN/Cu/FeN/FeMn multilayer.

• 한국자기학회지
• /
• 제16권4호
• /
• pp.193-196
• /
• 2006

제일원리적 국소 스핀밀도 근사에 의한 계산방법을 이용하여 Ni 나노와이어에 대한 전자구조와 자기적 성질을 연구하였다. 단위 세포당 Ni 원자의 개수(n = 1 − 4)에 따른 구조적 특성에 따라 각각의 나노와이어에 대한 결합에너지와 자기모멘트를 계산하였다. 계산결과 지그재그-사각형 $Ni_4$ 나노와이어가 에너지적으로 가장 안정하였다. 또한 Ni 나노와이어의 자기모멘트는 선형 나노와이어 Ni1가 $1.34 {\mu_B}/atom$ 로 가장 큰 값을 나타냈으며, 단위 세포당 원자 개수가 증가될수록 자기모멘트는 감소하여 사각형 나노와이어 $Ni_4$의 자기모멘트가 $0.91 {\mu_B}/atom$ 로 가장 작은 값을 나타냈다. $Ni_n$(n = 1 − 4)의 각각의 구조들에 대한 상태밀도, 에너지 띠 등의 전자구조 계산결과를 제시하고 논의 검토하였다.

• Journal of Magnetics
• /
• 제13권1호
• /
• pp.7-10
• /
• 2008

The structural and magnetic properties of functionalized carbon chains doped with 4d transition metals, such as Ru, Rh, and Pd, were investigated using the full-potential linearized augmented plane wave (FLAPW) method. The carbon nanowire doped with Ru exhibited a ferromagnetic ground state with a sizable magnetic moment, while those doped with Rh and Pd had nonmagnetic ground states. For the Ru-doped chain, the density of states at the Fermi level showed large spin polarization, which suggests that the doped nanowire could be used for spintronic applications.

• Journal of Magnetics
• /
• 제13권3호
• /
• pp.85-87
• /
• 2008

I report a simple method to correct the saturation effect in absorption spectra measured in total electron yield (TEY) mode. It does not require additional measurements of the X-ray penetration depth. In order to check the reliability of the method, X-ray magnetic circular dichroism (XMCD) spectra for polycrystalline Fe were measured at two different incident angles, and then processed with the method. The two resultant XMCD spectra were identical, and their sum rule analysis produced the ratios of orbital magnetic moment to spin magnetic moment, which were very close to the well-known value.

• Journal of Magnetics
• /
• 제13권4호
• /
• pp.124-127
• /
• 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.