• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.161-161
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• 2000

Ferromagnetic 3d 전이금속과 paramagnetic 5d 금속으로 이루어지진 Pt-Co 계는 자기이방적 (magnetic anisotropy) 성질로 인하여 많은 관심을 모으고 있는 계로서는 다층박막 및 합금박막에 대한 지기적 성질에 대한 많은 연구가 있어 왔다. 최근 sputtering method 에 의해 제작된 Pt-Co 합금박막에 대해 Ar 기체분압에 따라 보자력 (coercivity)이 변화되고 PMA (perpendicular magnetic anisotropy)를 갖는 것을 관측하였다. PMA의 근원은 주로 계면에서의 anisotropy 에너지와 관련이 있는 것으로 이해되기 때문에 합금박막의 경우는 PMA가 불가능한 것으로 여겨져 왔다. 그럼으로서 PMA에 대한 근원에 대한 명확한 해석이 필요하게 되었다. 또한 보자력(coercivity)은 불순물의 함량이 감소할수록, 그리고 내부적 변형이 제거될수록 감소하기 때문에, 계면 및 결정구조와 관련이 있는 것으로 알려져 있다. 이러한 자기적 특성을 관찰하고자 [Pt(51 )/Co(112 )]4, [Pt(90 )/Co(66 )]4, 그리고 [Pt(121 )/Co(30 )]4, 다층박막과 이들 박막을 80kV Ar+ 이온선 혼합후 박막의 결정성 변화를 관찰하기 위하여 GXRD (glancing x-ray diffraction) 스펙트럼을 얻어보았다. 그 결과 세 system 모두 disordered fcc 합금박막임을 확인하였다. fcc(111) 방향에 대한 평균 격자공간(lattice spacing)의 크기변화는 한층 당의 Co 두께가 두꺼울수록 거의 선형적으로 감소함을 볼수 있었다. MOKE 실험에 의하면, 이들 다층박막이나 합금박막의 경우 모두, in-plane 방향에 대해 자화 용이축(easy magnetization axis)을 가지고 있었다. 그리고 보자력의 크기에 있어서, 다층 박막의 경우에 있어서 Co 층에 두께 두꺼울수록 보자력의 크기가 감소하였지만 그림1에서와 같이 합금박막의 경우는 정반대로 Co층의 두께가 얇을수록 보자력의 크기가 감소함을 관찰하였다.

• Korean Journal of Logic
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• v.22 no.1
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• pp.1-23
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• 2019

Gott, Carter, Leslie, Bostrom and so on, as Descartes did, have made the evidence that is "I am here as an observer" to support many other beliefs. Bostrom and others who studied observation selection effects are missing two points. First, the self-consciousness information of the ones who just came up is distinct from that of the ones who have awoken. The awoken 'I' can trace back by memory to the past, but the 'I' who just came up can not. Second, when calculating credence, we must distinguish the ones in the possible worlds from the ones in the actual worlds. An estimate of credence where only one possible world is actualized among all possible worlds, differs fundamentally from that where all possible worlds are actualized. Keeping these two points in mind, we have explored what is the nature of the self-consciousness information of the one who just came up. We examine in depth the two human embryos thought experiment.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.13-17
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• 2004

We have investigated the effect of Hf insertion in the Al oxide tunnel barrier on the properties of magnetic tunnel junctions (MTJs). MTJs with Hf inserted barrier show the higher tunnel magnetoresistance (TMR) ratio and less temperature and bias voltage dependence of TMR than MTJs with a conventional Al$_2$O$_3$ barrier. The enhancement of TMR ratio and the reduction of the temperature and bias voltage dependence might be due to the reduction of defects in the barrier. Al-Hf oxide was formed by depositing Al and Hf simultaneously, and oxidizing the compound films. The TMR ratio of 36% was almost the same value as that with Hf inserted barrier. This implies that the inserted Hf layers mixed with Al layers during deposition or oxidation, and they might form Al Hf oxide barriers. This compound Al Hf oxide formation may be responsible to reduction of defect concentration which enhanced the TMR ratio and reduced temperature and bias-voltage dependence.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.289-292
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• 1993

[Ni/Fe/Cu] and [Fe/Ni/Fe/Cu] multilayers were prepared with three gun rf-magnetron sputtering, and dependence of magnetoresistance on the Ni IFe thickness ratio was investigated. Vaccum annealing was tried to invetigated the effect of annealing. Oscillation of magnetoresistance on the Cu spacer thickness was dbserved in these two kinds of multilayers. When the thickness of Fe inserted into the Ni/Cu interface was about $3\;\AA$. the maximum value of magnetoresistance(13 %) could be observed. In a sample of $1~2\;\AA$ Fe thickness, saturation field decreased significantly, while magnetoresistace decreased slightly in comparison with the sample of $3\;\AA$ Fe. In ${[Cu(23\;\AA)/Fe(1\;\AA)/Ni(18\;\AA)/Fe(1\;\AA)]}_{20}/Fe(80\;\AA)/Si$, 6 % magnetoresistance with 100 Oe saturation field could be obtained. No appreciable change in magnetoresistance and saturation field could be observed by low temperature annealing. Formation of Ni-Fe alloy was not confinred.

• Journal of Korean Society of Forest Science
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• v.105 no.2
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• pp.253-260
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• 2016

This study identified the effect of forest education on juvenile probationers' psychological and emotional changes. Changes of mood states, self-esteem, self-control of 77 juvenile probationers, who attended forest education program co-managed by Korea Forest Service and Ministry of Justice in 2015, were identified by self-report survey. The result came out that forest education program had influence on positive change of juvenile probationers' mood states, increase of self-esteem, pursuing long-term satisfaction. The significance of the study is that the positive effect of applying forest education to attendance order program of juvenile probation was identified.

• East Asian mathematical journal
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• v.23 no.3
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• pp.271-302
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• 2007

The purpose of this study is to study how effective teachers' self reflectiveness are on enhancing mathematics teaching activities. Researcher is the object of the study and relating preceding researches, establish some instruments for study. This research was examined for six times from fifth week of March to second week of May. In order to accomplish this study, one class of the first grade of high school in Ulsan was selected. In order to define the changes of teaching activity, the first lecture was practiced without analyzing or reflective activity. From the second lecture, analyze and reflect own teaching activity with recording. After finishing all lecture, distribute the recordings to observers and other teachers and then, get measured. Based on the results, self reflective teaching makes great effects on enhancing teachers' teaching activities. Through teachers' own reflective teaching, they can know their advantages and disadvantages, repeatable was of speaking, and the acknowledgement of objectives. And, finally, they can enhance their teaching activity by reflective teaching.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.251-255
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• 1999

NiFe(60 $\AA$)/Co(0$\AA$$\leq$x$\AA$$\leq$15$\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valve thin films were prepared on 4$^{\circ}$ tilt-cut Si(111) substrates with a 50 $\AA$ thick Cu underlayer without applying any external magnetic field during the deposition, and the effects of inserted ultrathin Co layer on magnetic anisotropy and GMR properties of the NiFe(60 $\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valves were investigated. As the ultrathin Co layer was inserted into the NiFe/Cu interface of the spin valves, GMR ratio was increased from about 1.5% to 3.5%, and the easy axis of NiFe(60 $\AA$) layer was rotated by 90$^{\circ}$. Accordingly, it was aligned along the same direction with the easy axis of Co(30 $\AA$)layer. Therefore, squared R-H curves was obtained in the spin valves, which is favorable properties for the digital GMR devices such as MRAM. In order to investigate the change of magnetic anisotropy of NiFe layer of the spin valves in more details,XRD measurement was performed using NiFe(500 $\AA$) and NiFe(500 $\AA$)/Co(10 $\AA$) thin films on the same templates. Strong (220) NiFe peak was observed in both films regardless of the inserted Co layer, so it was thought that the variation of magnetic anisotropy of NiFe layer is from the interface effect, the change of interface from NiFe/Cu to NiFe/Co, rather than the volume effect such as the change of magnetocrystalline effect.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.263-271
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• 1994

We have produced $Co_{1-x}Pt_{x}(X\;=\;0.53\;and\;0.75)$ alloy films by DC magnetron sputtering at various substrate temperatures and sputtering pressures. Sputter-deposited Co-Pt alloy films showed a strong (111) texture, and the degree of (111) texture of the as-deposited film was found to depend on the substrate temperature and Ar pressure. However, we observed that the degree of (111) texture did not affect the magnetic properties. In addition, we have investigated the effect of heat-treatment on magnetic properties of these films. While the magnetic properties of the $Co_{0.25}Pt_{0.75}$ alloy films showed no noticeable changes, the coercivities and the squarenesses of the $Co_{0.47}Pt_{0.53}$ alloy films were drastically increased by annealing. Structural analysis using transmission electron microscopy(TEM) and x-ray diffractornetry(XRD) revealed that $CoPt(L1_{0})$ and $CoPt_3(L1_{2})$ ordered phases, respectively, were formed, each with a strong (111) texture. By comparing the magnetic properties between $CoPt(L1_{0})$ and $CoPt_3(L1_{2})$ ordered phases in relation to the atomic arrangements in a unit cell, we conclude that the magnetic anisotropy in the Co-Pt alloy system depends mainly on the atomic arrangements of Co and Pt.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.83-83
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• 2003

자기 폭풍 발생시에 지구 자기권 내에서 MeV 에너지대의 전자 플럭스가 증가하는 현상이 나타남이 관측되었다. 이러한 Relativistic Electron Events (REE) 가속 기작의 주요 후보로 Ultra-Low Frequency(ULF)와 whistler 파동의 역할이 제시되어왔다. 본 연구에서는 1997부터 1999년에 발생한 대표적인 자기 폭풍들을 선택하여, 상대론적 전자 플럭스가 증가한 경우, 감소한 경우 그리고 변화가 크게 나타나지 않는 경우의 세 가지로 분류하여 보았다. 각각의 event들에 대해 CANOPUS 지상자기장 관측소에서 얻은 지자기 값을 이용하여 위 각각의 세 경우에 대해 ULF 파동의 크기 변화를 비교해 보았다. 그리고 똑같은 자기 폭풍 현상에서 POLAR 위성의 관측 값을 이용하여 whistler 영역의 파동 강도를 살펴보았다. 또한 자기 폭풍과 REE, 그리고 ULF의 변화가 L-shell값과 어떤 관련이 있는지도 알아본다.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.206-207
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• 2004

수직자기이방성을 갖는 [Co/Pt]$\times$5 다층박막을 상온에서 이온빔 증착(ion beam deposition)법으로 제작하여 자기적 및 열적 특성을 연구하였다. 수직자기이방성 특성은 비정상 홀(Hall)-전압법으로 측정하였으며, 표면광 Kerr 효과로 확인하였다. $[Co(10{\AA}/Pt(12.5{\AA})]{\times}5$) 다층박막에서 수직자성 보자력은 400 Oe이었고 수평자성은 매우 큰 곤란축(hard-axis) 특성을 유지하였다. 진공 열처리 시 1 kOe의 균일한 자기장이 박막면 수평(시료 A)과 수직(시료 B)이 되도록 각각 인가함에 따라 열적안정성을 관찰하였다. 시료 A의 수직자성의 보자력이이 $300^{\circ}C$에서 1 KOe로 유지되어 시료 B의 열적안정성 보다 훨씬 우수하였다.