• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.296.1-296.1
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• 2008

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.241.2-241.2
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• 2008

• Transactions on Electrical and Electronic Materials
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• 제16권6호
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• pp.342-345
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• 2015

The n -type Hf_0.25Zr_0.25Ti_0.5NiSn_0.998Sb_0.002 Half-Heusler (HH) alloy composition was prepared by using the induction melting method in addition to the mechanical grinding, annealing, and spark plasma sintering processes. Analysis of X-ray diffraction (XRD) results indicated the formation of a pure phase HH structured compound. The electrical and thermal properties at temperatures ranging from room temperature to 718 K were investigated. The electrical conductivity increased with increasing temperatures and demonstrated nondegenerate semiconducting behavior, and a large reduction in the thermal conductivity to the value of 2.5 W/mK at room temperature was observed. With the power factor and thermal conductivity, the dimensionless figure of merit was increased with temperature and measured at 0.94 at 718 K for the compound synthesized by the induction melting process.

• Journal of Magnetics
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• 제12권3호
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• pp.97-102
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• 2007

We have investigated the electronic structures and magnetism of a full Heusler alloy $Co_2CrGa(001)$ surface by using the all-electron full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA). We considered two types of different terminations: the Co-terminated (Co-Term) and the CrGa-terminated (CrGa-Term) surfaces. From the calculated layer-projected density of states (LDOS), we found that the surface of the CrGa-Term shows nearly half-metallic character while that of the Co-Term is far from the half-metallic. For the Co-Term, the surface Co atom moves down to the bulk region by $0.05{\AA}A$, while the subsurface Cr and Ga atoms move up to the surface layer by 0.05 and $0.01{\AA}$, respectively. For the CrGa-Term, there is a large inward relaxation of the surface Ga atom $(0.07{\AA})$, but the relaxation of the surface Cr atom is very small $(0.01{\AA})$. The relaxations affect not much to the overall shapes of DOS for both terminations, but make the surface states of the surface Cr and Ga atoms for the CrGa-Term shift to higher energy that enhances the nearly half-metallic character of the CrGa-Term. The magnetic moments of the surface $Cr(2.98{\mu}_B)$ in the CrGa-Term and the surface $Co(1.17{\mu}_B)$ in the Co-Term were much increased compared to those of the inner-layers $(1.79\;and\;0.77{\mu}_B)$, respectively, while that of the subsurface Cr atom in the Co-Term was decreased to $1.19{\mu}_B$.

• 한국자기학회지
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• 제26권6호
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• pp.185-189
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• 2016

이 연구에서는 방사광을 이용한 연 X-선 흡수 분광법(soft X-ray absorption spectroscopy: XAS)과 광전자 분광법(photoemission spectroscopy: PES) 을 이용하여 반쪽금속 반강자성체 후보 물질인 $Mn_3Ga$ 호이슬러 화합물의 전자구조를 연구하였다. 이 연구에 사용된 시료는 full-Heusler $Mn_3Ga$로 ball milling 후 열처리하지 않은 시료와 ball milling 후 $400^{\circ}C$에서 열처리한 두 시료를 사용하였다. XAS 분석에 의하면 $Mn_3Ga$에서 Mn 이온들의 원자가는 $Mn^{2+}$ 상태임을 알 수 있었으며, 국소적으로 팔면체 대칭성을 가진 Mn 이온들과 사면체 대칭성을 가진 Mn 이온들이 섞여 있음을 알 수 있었다. 그리고 $Mn_3Ga$의 가전자띠 PES 스펙트럼은 전자구조 계산에 의한 반쪽 금속성 상태밀도와 대체로 유사함을 발견하였다.

• 한국재료학회지
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• 제6권1호
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• pp.90-98
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• 1996

Mn((Cu0.66AI0.34)1-x(Bi0.3Sb0.7)x) 및 Mn((Fe0.66AI0.34)1-x(Bi0.3Sb0.7)x) 합금계의 상의 변화와 자기적 특성을 조사하였다. Mn((Cu, SI)(Bi, Sb)) 합금계는 Bi상, MnSb상, MnBi상, k-상, Heuser상, Mn2Sb 및 $\beta$-Mn상의 혼합상으로 이루어졌으며 x가 증가함에 따라 Bi상과 Mn2Sb상이 증가하고 K-상, Heusler상 및 $\beta$-Mn상이 줄어들거나 사라졌다. 자기적 성질은 자성을 띄는 MnSb상, MnBi상, Mn2Sb상, k-상 및 Hseusler상과 비자성인 Bi상과 $\beta$-Mn상의 상대적 분율에 의해 결정됨을 알 수 있었고, 150K-200K 부근에서 그 이하로 온도가 감소함에 따라 자화값이 급격히 감소하는 현상이 나타났다. Mn((Fe, AI)(Bi, Sb))합금계는 Bi상, MnSb상, MnBi상, MnBi상,$\beta$-Mn상, k-상 및 Mn2Sb상의 혼합상으로 나타났으며, 자기적 성질은 조사한 전 조성에서 강자성을 띄고 있음을 알 수 있었다.

• Journal of Magnetics
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• 제13권2호
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• pp.43-52
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• 2008

The objective of this paper is to review the magnetic and magneto-transport properties of Co/$Co_2TiSn$ consisting of two metallic magnetic phases that are antiferromagnetically exchange-coupled at the phase boundary. The bulk Co/$Co_2TiSn$ system, which has a $Co_2$TiSn Heusler alloy precipitates in the hexagonal Co matrix, showed an unusual coercivity change with a concurrent change in temperature, and was modeled on the basis of a wall formation caused by exchange coupling at the phase boundary. For measurements of magneto-transport properties, Co/$Co_2TiSn$ thin films that had two-magnet phases were deposited using a magnetron sputtering system with a composite target. The magnetization process in the films is also explained on the basis of the model of wall formation at the phase boundary. Annealed Co/$Co_2TiSn$ films showed a 0.12% GMR effect, indicating the scattering of polarized conduction electrons due to the antiparallel exchange coupling at the phase boundary. The scattering process of conduction electrons at the phase boundary was modeled with relation to the magnetization process.