• Journal of Magnetics
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• 제13권4호
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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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• 제16권1호
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• pp.23-26
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• 2011

The effects of titanium ions on the crystallographic and spin-rotation transitions in iron sulfide have been examined by M$\"{o}$ssbauer spectroscopy in the temperature range of 78 to 600 K. It is noted that the titanium impurity of $Ti_{0.02}Fe_{0.98}S$ affects both the crystallographic and spin-rotation transitions of the iron sulfide. 2% impurity of $Ti^{2+}$ in FeS causes the increase in the difference between the spin rotation and ${\alpha}$ transition temperature by as much as 10 K compared with that for FeS. Both 1c and 2c structures coexist in the range between the ${\alpha}$ transition temperature and approximately 26 K, with a smaller hyperfine field corresponding to the 1c structure. The spin-rotation temperature for $Ti_{0.02}Fe_{0.98}S$ was measured to be 365 K, which is 10 K lower than the ${\alpha}$ transition temperature. By the 2% impurity of $Ti^{2+}$ in FeS the N$\'{e}$el temperature appreciably is not affected.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2009년도 정기총회 및 동계학술연구발표회
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• pp.72-73
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• 2009

First-principles calculations were carried out to investigate the effects of Al impurities on bcc Fe magnetism by considering SOC. No significant solid solution hardening effect was found. Albeit the effects of the SOC by Al on spin magnetic moments were minor, there are sizeable orbital magnetic effects. It is concluded that the orbital magnetism due to the Al impurity is strongly related with the impurity screening of the system as seen in Si impurity case [3], but the effects of Al impurity is stronger than those of Si impurity in terms of orbital magnetism.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.277-284
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• 2004

Low carbon steels containing Si of up to $1.2\;wt\%$ were oxidized in air at 1373 K and 1523 K, i.e. below and above the eutectic temperature of FeO and $Fe_2SiO_4$. The influence of a impurity element, S on behavior of scale formation during oxidation was investigated by using $M\"{o}chssbauer$ spectroscopy and EDS. This allowed establishment of an interface oxidation model of Si-added steel depending on temperature and an impurity element. A compound of FeO and FeS was formed in the scale/matrix interface of low carbon steels containing S of up to $0.03\;wt\%$ oxidized above 1213 K of the eutectic temperature. This was flat formed between $Fe_2SiO_4$ nodules along the scale/matrix interface without selective oxidation. It is due to low viscosity and high wettability of the compound of FeO and FeS in liquid. Conventional metallographic examinations revealed that roughness of the scale/matrix interface in Si-added steels became flat as the content of S increased. It was independent of oxidizing temperature and Si content. Effects of oxidizing temperature and an impurity element content on descaling characteristics in Si-added steels were evaluated by using a hydraulic descaling simulator. Good descaling characteristics was attributable to this flatness of the scale/matrix interface.

• 한국전기전자재료학회논문지
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• 제16권6호
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• pp.532-537
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• 2003

Crystallographic, electric, magnetic and heat transition properties of $\alpha$-Fe$_2$O$_3$ have been studied with a small addition of Eu impurities. Hematite($\alpha$-Fe$_2$O$_3$) is a basic ferromagnetic material having rhombohedral structure, which is similar to perovskites structure. Eu is a rare earth element that has an electric configuration of 4f$^{7}$ 6s$^2$. X-ray diffraction pattern of Fe$_{1-x}$ Eu$_{x}$O$_3$ (x = 0.00, 0.04, 0.06) shows an increament of a value when the amount of Eu impurities increased. The VSM data show an increment of magnetization by increasing the amount of Eu impurity. The one with x=0.06 shows the largest increment of magnetic remanence. The magnetic remanence varied from 0.49$\times$10$^{-3}$ emu/g to 0.62$\times$10$^{-3}$ emu/g when Eu impurity is increased by 2 %. Coercivity is decreased as Eu impurity is increased. Resistances is reduced significantly by Eu impurity. There is a clear difference in temperature-dependent resistance depending on the amount of Eu impurities. Especially, there are cusps between 150 K to 175 K. It indicates the change of electronic quantum states inside the atoms by rare earth impurities in rhombohedral structure. Temperature-dependent heat capacity shows that the most effective amount of Eu impurities is 6 %. %.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.195-196
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• 2007

In this paper, we investigated impurity content of carbon nanotube reinforced semiconductive shield materials and conventional semiconductive shield materials in power cables. To reduce impurity content, we used solution compounding method that an adding process of extra additives neglected. Impurity content measured through ICP-AES(Inductively Coupled Plasma Atomic Emission Spectroscopy). Also, impurity measured Ca, Cu, Fe, Al, Mg, Na, K, Si in eight. As a result, carbon nanotube reinforced semiconductive shield materials is lower than conventional semiconductive shield materials in impurity content by ICP-AES.

• Journal of Magnetics
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• 제16권1호
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• pp.1-5
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• 2011

The magnetism and electronic structure of bcc $Al_1Fe_{26}$ was investigated by means of first-principles calculations with and without spin-orbit coupling (SOC). From the calculated total energy, the SOC corrected system is shown to be approximately 5 meV per atom lower than the SOC uncorrected system. The induced spin magnetic moment at the Al site was -0.125 ${\mu}_B$ without SOC and -0.124 ${\mu}_B$ with SOC. The orbital magnetic moments were calculated to be 0.002 ${\mu}_B$ in [$\overline{1}$00] direction for Al. The electronic structures showed the nearest neighbor antiferromagnetic interaction between Fe and Al to be essential for determining the magnetism of the $Al_1Fe_{26}$ system.

• 한국자기학회지
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• 제18권6호
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• pp.211-216
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• 2008

Si이 체심입방구조(body centered cubic; bcc) Fe에 불순물로 포함된 경우에 Fe의 전자구조와 자성에 미치는 영향을 스핀-궤도 상호작용(spin-orbit coupling, SOC)을 고려한 제일원리방법을 통하여 연구하였다. Si 불순물의 효과를 기술하기 위하여 27개의 원자가 포함된 bcc Fe 초격자 구조를 고려하였다. 제일원리방법은 전전자 총퍼텐셜선형보강평면파(all-electron full-potential linearized augmented plane wave, FLAPW) 방법을 일반기울기 근사(generalized gradient approximation, GGA) 하에서 계산하였다. 스핀-궤도 상호작용은 스핀대각항 만을 고려한 이차변분방법을 이용하여 자체충족적으로 계산하였다. SOC를 고려하지 않은 강자성(ferromagnetic, FM) 상태의 경우 Si 불순물의 경우에는 $-0.143{\mu}B$의 스핀 자기모멘트가 계산되었으며, Fe 원자가 Si 불순물에서 멀어지면서 각각 $2.214{\mu}B$, $2.327{\mu}B$, 및 $2.354{\mu}B$의 값을 얻었다. 그러나, SOC를 고려한 경우 Si 불순물의 스핀 자기모멘트는 $-0.144{\mu}B$로 계산되어 SOC의 효과가 크지 않았으나, Fe 원자의 경우 각각 $2.189{\mu}B$, $2.310{\mu}B$, 및 $2.325{\mu}B$로 계산되어 SOC를 고려한 경우 스핀 자기모멘트 값이 줄어드는 것을 알 수 있었다. 총전하 및 스핀밀도의 비교와 상태밀도의 비교를 통하여 이러한 현상은 Si 불순물에 의한 영향을 가리는데 참여하는 Fe 원자의 $t_{2g}$ 전자 궤도의 변형의 효과로서 SOC를 고려할 때만 얻을 수 있다.

• 한국자기학회지
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• 제24권3호
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• pp.71-75
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• 2014

정비조성으로 성장시킨 $LiTaO_3$ 단결정 및 비정비조성으로 성장시킨 $LiTaO_3$ 단결정 내에 불순물로 도핑된 $Fe^{3+}$ 상자성 불순물 이온의 바닥 상태에서의 에너지 준위를 계산하였다. $LiTaO_3$ 단결정 내에서 육방정계 대칭성을 갖는 $Fe^{3+}$ 이온의 전자 상자성 공명 상수인 분광학적 분리인자 g 및 영자기장 갈라지기 D 값을 이용하여 6개의 에너지 준위 사이의 에너지 준위를 계산하였다. 자기장을 결정학적 주축 ([100], [001], [111])과 나란하게 가하여 자기장을 증가시켜 감에 따라 얻은 에너지 준위 갈라지기는 자기장을 가한 방향에 따라서 서로 다른 값을 나타내었다. ${\mid}{\pm}5/2$ > ${\leftrightarrow}{\mid}{\pm}3/2$ >및 ${\mid}{\pm}3/2$ > ${\leftrightarrow}{\mid}{\pm}1/2$ > 사이의 전이에서 계산한 영자기장 갈라지기 값은 정비조성으로 성장시킨 $LiTaO_3$ 단결정과 비정비조성으로 성장시킨 단결정의 경우에 각각 12.300 GHz, 6.150 GHz와 59.358 GHz, 29.679 GHz이다. 결정성장 조건에 따라 에너지 준위가 상당히 다른 것으로 나타났다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
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• pp.49-49
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• 2001