• 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 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.17-17
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• 2003

Semiconductors with ferromagnetism at room temperature has been actively searched for in recent years; a prospect of devices using both charge and spin continuously gives impetus to the activities. Transition metal doped oxide materials have been of particular interest. Co substituted ZnO [1] and TiO$_2$ [2] thin films, for example, were reported to show ferromagnetic properties at room temperature. However, various studies do not seem to converge on a definite picture [3,4,5]. The issue is rather fundamental: whether a system shows ferromagnetic properties at all, and in case it does, whether the system possesses a close coupling between magnetism and transport properties. In this talk, we shall assess the current status of transition metal doped oxide materials as room temperature ferromagnetic semiconductors.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.461-461
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• 2000

We have investigated electronic structuresof antiferromagnetic YBaCo_2O_5 using the local spin-density approximation (LSDA) + U method. The charge and orbital ordered insulating ground state is correctly obtained with the strong on-site Coulomb interaction. Co^{2+} and Co^{3+} ions are found to be in the high spin (HS) and intermediate spin (IS) state, respectively. The tetragonal to orthorhombic structural transition is responsible for the ordering phenomena and the spin states of Co ions. The large contribution of the orbital moment to the total magnetic moment indicates that the effect of the spin-orbit coupling is very important in YBaCo_2O_5.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.240.2-240.2
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• 2007

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.82.1-82.1
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• 2008

• 한국자기학회지
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• 제21권1호
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• pp.1-4
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• 2011

정육면체 전이금속 산화물 FeO, MnO의 자기적 상호작용을 제1원리의 범밀도함수법을 이용하여 계산하였다. 그 결과, 모두 초교환작용으로 인해 반강자성적 상호작용이 가장 낮은 에너지를 가지고 있었다. 자기이방성은 반강자성 스핀 배열의 FeO 클러스터에서만 발견되었다. 그 원인은 <111> 방향으로 각운동량을 가지는 3d down-spin 전자의 스핀-궤도 결합에 기인하였다.

• Progress in Superconductivity
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• 제11권2호
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• pp.112-117
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• 2010

We examine phase transition of the spin density wave and $\pi$ phase shifted superconductivity in the Fe pnictide superconductors. The phase diagram is described in the plane of the temperature T and the doping x with the combination of Ginzburg-Landau expansion of the free energy near the multi-critical temperature $T_c$ and the self-consistent numerical iterations of the gap equations. The phase separation or coexistence is determined by computing the 4-th order terms of the free energy which is confirmed by the numerical calculations. We can show the phase coexistence when the spin density wave is incommensurate. And the first order phase transition is observed near the boundary between commensurate and incommensurate spin density wave.

• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.4005-4010
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• 2011

We investigated thermal behavior of spin-coated films of P(HB-co-HHx)/PEG blends by using infraredreflection absorption (IRRAS) spectroscopy and 2D correlation spectroscopy. Based on 2D IRRAS correlation spectra, we could determine the sequence of spectral intensity changes with increasing temperature that PEG band changes first and then a band for crystalline component of P(HB-co-HHx) changes before a band for amorphous component. The intensities of bands for PEG and amorphous P(HB-co-HHx) were changed greatly as PEG weigh % of P(HB-co-HHx)/PEG blends increased. Transition temperatures of P(HB-co-HHx)/PEG blends were successfully determined by 2D gradient mapping method. The transition temperature of spincoated films of 98/2 and 90/10 P(HB-co-HHx)/PEG blends and 80/20 P(HB-co-HHx)/PEG blend determined by 2D gradient map are, respectively, about 137.5 and $132.5^{\circ}C$. Furthermore, P(HB-co-HHx)/PEG blends show an additional transition temperature that have been interpreted in terms of different lamellar thicknesses in spin coated films.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.104.1-104.1
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• 2007

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2009년도 임시총회 및 하계학술연구발표회
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• pp.53-54
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• 2009