• Journal of Magnetics
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• 제11권1호
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• pp.8-11
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• 2006

Recently half-metallic full-Heusler alloy films have attracted significant interests for spintronics devices. As these alloys have been known to have a high spin polarization, very large TMR ratio is expected in magnetic tunnel junctions. Among these alloys, $Co_2MnSi$ full-Heusler alloy with a high spin polarization and a high Curie temperature is considered a good candidate as an electrode material for spintronic devices. In this study, the magnetic and structural properties of $Co_2MnSi$ Heusler alloy films were investigated. TMR characteristics of magnetic tunnel junctions with a $Co_2MnSi/SiO_2/CoFe$ structure were studied. A maximum MR ratio of 39% with $SiO_2$ substrates and 27% with MgO(100) substrates were obtained. The lower MR ratio than expectation is considered due to off-stoichiometry and atomic disorder of $Co_2MnSi$ electrode together with oxidation of the electrode layer.

• 반도체디스플레이기술학회지
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• 제19권3호
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• pp.49-54
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• 2020

We studied the electronic and magnetic properties for the Mn-doped chalcopyrite (CH) AlAs, GaAs, and AlGaAs₂ semiconductor by using the first-principles calculations. The chalcopyrite AlGaP₂, AlGaAsP, and AlGaAs₂ compounds have a semiconductor characters with a small band-gap. The interaction between Mn-3d and As-4p states at the Fermi level dominate rather than the other states. The ferromagnetic ordering of dopant Mn with high magnetic moment is induced due to the Mn(3d)-As(4p) strong coupling, which is attributed by the partially filled As-4p bands. The holes are mediated with keeping their 3d-electrons, therefore the ferromagnetic state is stabilized by this double-exchange mechanism. We noted that the ferromagnetic state with high magnetic moment is originated from the hybridized As(4p)-Mn(3d)-As(4p) interaction mediated by the holes-carrier.

• Journal of Magnetics
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• 제13권4호
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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.

• 한국자기학회지
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• 제17권4호
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• pp.147-151
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• 2007

호이슬러 구조를 가진 반쪽금속 $Co_2$ZrSi와 반도체인 ZnTe이 (001)면을 따라 계면을 이루었을 때 전자구조, 자성 및 반쪽금속성을 총 퍼텐셜 선형보강평면파동(FLAPW) 방법을 이용하여 이론적으로 연구하였다. 모두 4가지 가능한 계면, 즉 ZrSi/Zn, ZrSi/Te, Co/Zn와 Co/Te을 고려하였다. 계산된 상태밀도로부터 4가지 계면에서 모두 반쪽금속성이 깨어졌음을 알 수 있었으나 Co/Te의 경우 페르미에너지에서 소수 스핀 상태밀도의 값은 영에 가까웠다. 계면에서 반쪽금속성이 파괴되는 것은 계면에서 원자들의 좌표수와 대칭성이 덩치상태와 달라지고 계면전자들 사이의 띠 혼성에 의해 덩치 $Co_2$ZrSi의 소수 스핀 띠간격에 계면상태들이 나타났기 때문이다. Co/Te의 계면에서 Co원자의 자기모멘트의 값은 "bridge"와 "antibridge" 위치에서 각각 0.68과 $0.78{\mu}_B$로서 이는 덩치 Co경우의 값($1.15{\mu}_B$)에 비하여 크게 감소한 것이다. Co/Zn에서 "bridge"와 "antibridge" 위치에 있는 Co원자의 자기모멘트는 각각 1.16과 $0.93{\mu}_B$의 값을 가졌다. 반면 ZrSi/Zn와 ZrSi/Te의 경우 계면 바로 밑층의 Co원자들은 $1.13{\sim}1.30\;{\mu}_B$ 사이의 자기모멘트를 가졌는데 이는 덩치 $Co_2$ZrSi에서의 값과 비슷하거나 약간 증가한 값이다.