• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.955-956
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• 2006

Fe-doped $TiO_2$ nanopowders were prepared by mechanical alloying (MA) varying Fe contents up to 8.0 wt.%. The UV-vis absorption showed that the UV absorption for the Fe-doped powder shifted to a longer wavelength (red shift). The absorption threshold depends on the concentration of nano-size Fe dopant. As the Fe concentration increased up to 4 wt.%, the UV-vis absorption and the magnetization were increased. The benefical effect of Fe doping for photocatalysis and ferromagnetism had the critical dopant concentration of 4 wt.%. Based on the UV absorption and magnetization, the dopant level is localized to the valence band of $TiO_2$.

• 한국자기학회지
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• 제7권1호
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• pp.55-67
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• 1997

이중 교환작용은 전도전자와 자성을 가진 이온들의 상호작용에 의해 강자성이 나타나는 현상이다. 이중 교환작용의 가장 중요한 특성은 전도도와 자성이 직접적인 관계를 가진다는 것이다. 이것은 최근 산화 망간 계열의 화합물에서 관측되는 초거대 자기저항(CMR : colossal magnetoresistance)과 관련하여 많은 관심을 모으고 있다. 이 논문에서 우리는 이중교환이 무엇인지을 설명하고 이에 관한 고전적인 논의들을 정리하였다.

• Journal of Magnetics
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• 제12권3호
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• pp.108-112
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• 2007

Nature of phase transition in $LaVO_3$ has been studied using X-ray diffraction, SQUID magnetometer, and $M\"{o}ssbauer$ spectroscopy with 1% of $^{57}Fe$ doped sample. The crystal structure was orthorhombic with space group Pnma. Antiferromagnetic phase transition temperature $T_N$ was 140K, below which a weak ferromagnetic trace has been found. $M\"{o}ssbauer$ spectra below $T_N$ were single set of hyperfine sextet, which enabled us to discard the possibility of two inequivalent magnetic sites or uncompensated antiferromagnetism. Hyperfine magnetic field abruptly disappeared as low as about 90K, much below $T_N$.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.146-147
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• 2002

III-V magnetic semiconductors initiated by GaMnAs growth at low temperatures via molecular beam epitaxy (MBE) has been a hot issue recently for their possible application to spntronics. GaMnN may be one of the candidates for room temperature operating ferromagnetic semiconductors as proposed by a theoretical calculation, However, since GaN was grown at very high temperatures above ∼750$^{\circ}C$ even with MBE, it is expected that the incorporation of Mn into GaN will be limited. (omitted)

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.150-152
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• 2005

We investigated the fabrication and characteristics of spin-polarized LEDs based on GaN using (Ga,Mn)N as spin injection source. (Ga,Mn)N thin films were found to exhibit the ferromagnetic ordering above room temperature and the negative MR up to room temperature. The electrical characteristics in spin LEDs did not degraded in spite of the insertion of (Ga,Mn)N films. In EL spectra of spin LEDs, it is confirmed that spin LEDs emit the strong light at 7 K as well as room temperature. These results suggest that it is possible to emit spin-polarized light in our spin LEDs.

• Bulletin of the Korean Chemical Society
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• 제7권2호
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• pp.102-105
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• 1986

Samples with the nominal composition of $Co_{9-x}M_xS_8$(M = Ni, Rh, Ru, and Fe) were prepared, and their magnetic properties were measured. X-ray diffraction analysis showed that small amount of the elements Ni, Rh, and Fe could be incorporated into $Co_9S_8$ forming a homogeneous ${\pi}$-phase, whereas the Ru-incorporated sample could not be prepared in a single phase. The lattice parameter was observed to increase as other elements were incorporated into $Co_9S_8$. Samples incorporated with the elements of Ni, Rh, and Ru showed Pauli-paramagnetism while the Fe-incorporated sample exhibited weak ferromagnetism. The values of magnetic susceptibility for the Ni, Rh, Ru-incorporated samples were nearly the same as that of pure $Co_9S_8$.

• Journal of Magnetics
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• 제10권3호
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• pp.103-107
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• 2005

Magnetotransport is a prerequisite to realization of electronic operation of spintronic devices and it would be more useful if realized at room temperature. The effects of Be codoping on GaMnAs on magnetotransport were investigated. Mn flux was varied for growth of precipitated GaMnAs layers under a Be flux for degenerate doping via low-temperature molecular beam epitaxy. Magnetotransport as well as ferromagnetism at room temperature were realized in the precipitated GaAs:(Mn,Be) layers. Codoping of Be was shown to promote formation of MnGa clusters, and annealing process further stabilized the cluster phases. The room-temperature magnetic properties of the layers originate from the ferromagnetic clusters of MnGa and MnAs embedded in GaAs. The degenerately doped metallic GaAs matrix allowed the visualization of the magnetotransport through anomalous Hall effect.

• Journal of Magnetics
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• 제12권2호
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• pp.68-71
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• 2007

Even a pure bulk Fe has a complicated magnetic phase and its magnetism is still needed to be clarified. In this study we investigated the magnetism of bcc and fcc bulk Fe with total energy calculations as functions of atomic volume. The full-potential linearized augmented plane wave method was adopted within a generalized gradient approximation. The ground state of bulk Fe is confirmed to be of ferromagnetic (FM) bcc. For fcc structured Fe an antiferromagnetic (AFM) state is more stable compared to FM states which exist as low spin and high spin states. The stable AFM states were found to accompany a tetragonal distortion, while the FM states remained in a cubic symmetry. At an expanded lattice constant a high spin FM state was calculated to be able to be stabilized with significant enhanced magnetic moment compared to the value of the ground state, bcc FM.

• 한국결정성장학회지
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• 제31권3호
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• pp.112-115
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• 2021

Herein, a correlation between B-site cation order and spin-phonon coupling in La₂NiMnO₆ double perovskite has been investigated. Raman spectra of La₂NiMnO₆ double perovskite annealed at 950 and 1400℃ have been measured in the 140-598 K range. A substantial softening of the phonon modes has been observed below the Curie temperature, which emphasized the presence of the spin-phonon coupling in the system. The spin-phonon coupling was found to be stronger in relatively more ordered La₂NiMnO₆ double perovskite. Thus, the magnitude of spin-phonon coupling was influenced by the Ni/Mn cation order.

• 한국자기학회지
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• 제21권3호
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• pp.93-98
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• 2011

Laser Molecular-Beam Epitaxy 방법을 사용하여 $La_{0.35}Pr_{0.35}Ca_{0.3}MnO_3$(LPCMO)/$LaAlO_3$(LAO) 초격자를 성공적으로 증착하였으며 이의 열처리 전후 결정학적, 자기적 특성을 LPCMO 단층박막, 그리고 LPCMO/$SrTiO_3$(STO) 초격자와 비교 분석하였다. LPCMO 단층박막, 그리고 LPCMO/STO 초격자 단층박막의 경우, 표면이 열처리 전후 모두 거친 양상을 보인 것과는 달리 LPCMO/LAO 초격자 박막은 열처리 전후 모두 상대적으로 매우 매끈하였다. 열처리 후 단층박막, 초격자 박막 시료 모두 강자성 특성이 향상되었으며 특히 초격자의 경우에는 이러한 현상이 두드러졌다. 열처리 후에 보자력과 포화자기장이 감소하는 LPCMO 단층박막과는 달리 LPCMO/LAO 초격자의 경우, 열처리 후에도 보자력은 열처리 전과 같은 값을 보였으며 단층박막과는 반대로 포화자기장은 오히려 증가하였다. 이러한 자기적 특성은 절연체 사이에 강자성체가 끼여 있는 초격자라는 결정구조에서 기인하는 것으로 이해된다.