• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.236.2-236.2
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• 2007

• Journal of Magnetics
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• 제2권3호
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• pp.72-75
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• 1997

The temperature dependent saturation magnetization curve of amorphous Fe67 Co18B14Si1, alloy was measured using a SQUID magnetometer and vibrating sample magnetometer from 5 K up to 800 K. Inelastic neutron neutron scattering measurements also have been used to study the long wavelength spin dynamics of this high Tc amorphous ferromagnetic alloy. The magnon dispersion curve exhibit the conventional quadratic relationship E = D (T) q2 + $\Delta$, typical of an iso=obtained from a low temperature magnetization curve, which was consistent with the value obtained from the analysis oif inelastic neutron scattering data after consideration of its temperature dependence.

• Journal of Magnetics
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• 제12권3호
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• pp.118-123
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• 2007

We have studied the effect of Au-Cu back layer system ${\sim}10{\AA}$ thick on the properties of a spin valve. The back layers were Cu, Au, co-sputtered $Cu_xAu_{1-x}$, laminated $[Au/Cu]_n$. and bi-layer [Au/Cu]. When Au was added to the Cu, the resistance of the spin valve abruptly increased most likely due to impurity scattering. The GMR values were not increased significantly for all the structures. In the case of co-sputtered $Cu_xAu_{1-x}$, the changes in the resistance, ${\Delta}R$, was increased at a composition of ${\sim}Au_{0.5}Cu_{0.5}$. This increase in ${\Delta}R$ is due to increase in the resistance and not from the enhanced spin-dependent scattering. The structural analyses showed that the orthorhombic $Au_{0.5}Cu_{0.5}$ was formed in the back layer instead of the face-centered tetragonal $Au_{0.5}Cu_{0.5}$ as we expected. Thermal annealing over $400^{\circ}C$ may be required to have face-centered tetragonal in the $10{\AA}$ thick ultra-thin film. In the case of a laminated or bi-layered back layer, the properties of the spin valve were improved, which may be attributed to the increase in the mean free path of conduction electrons.

• 한국자기학회지
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• 제17권5호
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• pp.210-214
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• 2007

저차원 구조체에서 스핀의존산란에 의한 거대자기저항의 주요 연구들을 정리하였다. 본 논문에서는 다층박막, 나노선, 그리고 나노필러 등의 저차원 구조체에서 효율적인 자기저항의 제어에 대한 연구결과들을 양자역학적 차원에서 되 집어 보고 앞으로 스핀트로닉스 분야의 연구가 나갈 방향에 대해 논의하고자 한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.60-60
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• 2011

Giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and magnetic random-access memory (MRAM) are currently active research areas in spintronics. The high magnetoresistance and the high spin polarization (P) of electrons in the ferromagnetic electrodes of tunnel junction or intermediate layers are required. Magnetite, Fe3O4, is predicted to possess as half-metallic nature, P ~ 100% spin polarization, and has a high Curie temperature (TC~850 K). Experiments demonstrated that the P~($80{\pm}5$)%, ~($60{\pm}5$)%, and ~40-55% for epitaxial (111), (110) and (001)-oriented Fe3O4 thin films, respectively. Epitaxial Fe3O4 films may enable us to investigate the effects of half metals on the spin transport without grain-boundary scattering.In addition, it has been reported that the Verwey transition (TV, a first order metal-insulator transition) of 120 K in bulk Fe3O4 is strongly affected by many parameters such as stoichiometry and stress, etc. Here we report that the growth modes, magnetism and transport properties of Fe3O4 thin films were strongly dependent on the oxygen pressure during film growth. The average roughness decreases from 1.021 to 0.263 nm for the oxygen pressure increase from $2.3{\times}10-7$ to $8.2{\times}10^{-6}$ Torr, respectively. The 120 K Verwey transition in Fe3O4 was disappeared for the sample grown under high oxygen pressure.

• 한국자기학회지
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• 제8권5호
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• pp.288-294
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• 1998

기판/Ta/NiFe/Cu/NiFe/FeMn/Ta 스핀밸브에서 Ta 성막 후에 자유층 NiFe 스퍼터 증착시 가해진 기판 바이어스 전압에 의해 야기된 Ta/NiFe 계면에서의 원자섞임이 자기저항에 미치는 영향에 대해 조사하였다. 최대 자기 저항비 (MR ratio)를 나타내는 자유층의 적정두께는 바이어스 전압이 증가함에 따라 증가하였다. 이러한 현상의 원인은 바이러스 전압이 증가함에 따라 Ta과 NiFe의 원자섞임으로 계면에 있는 NiFe층 일부가 약한 강자성 또는 상자성화되어 스핀 비의존 산란을 하는 원자섞임층의 두께가 증가하였기 때문이다. 원자섞임층의 존재는 전기저항 변화와 자화량 변화로부터 증명하였다. 또 본 실험에서 비록 NiFe 증착시 기판 바이어스 전압이 변화더라도 최대 자기저항비를 갖는 최적 "유효" 자유층 두께는 기판 바이어스 전압에 무관하게 일정하였다.관하게 일정하였다.

• BMB Reports
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• 제42권4호
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• pp.223-226
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• 2009

We measured the pH-induced spectral changes of yeast iso-1-cytochrome c on silver nanoparticle surfaces using surface-enhanced resonance Raman scattering (SERRS) at 457.9 nm. At a pH of ~3, the Met80 ligand in yeast iso-1-cytochrome c is assumed to dissociate, leading to a marked conformational change as evidenced by the vibrational spectral shifts. The Soret band at ~410 nm in the UV-Vis spectrum shifted to ~396 nm at pH~3, indicating a transition from a low spin state to a high spin state from a weak interaction with a water molecule. Thus, SERRS spectroscopy can measure the pH-induced denaturalization of cyt c adsorbed on metal nanoparticle surfaces at a lower concentration with a better sensitivity than ordinary resonance Raman spectroscopy.

• Journal of Magnetics
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• 제6권1호
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• pp.1-4
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• 2001

We have used acetic acids ethanol and distilled water as a solvent to synthesize $La_{2/3}Sr_{1/3}Mn_{0.99}{^{57}}Fe_{0.01}O_3$(LSMFO) precursor. Crack-free LSMFO granular polycrystalline thin films have been deposited on thermally oxidized silicon substrates by spin coaling. The dependence of crystallization, surface morphology, magnetic and transport properties on annealing temperature was investigated. With increasing annealing temperature, the metal-semiconductor (insulator) transition temperature and the magnetic moment decrease while the resistivity increases. The lattice constants remain almost unchanged. For LSMFO thin films, spin-dependent interfacial tunneling and/or scattering magnetoresistance were observed. Our results indicate that the annealing temperature is very important in determining the intrinsic and extrinsic magnetotransport properties.

• Journal of Magnetics
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• 제17권4호
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• pp.265-270
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• 2012

We report improved low-field magnetoresistance (LFMR) effects of the $La_{0.7}Sr_{0.3}Mn_{1+d}O_3-Mn_3O_4$ composite films with the nominal composition of $La_{0.7}Sr_{0.3}MnO_3$(LSMO)-50 mol% $Mn_3O_4$. The composite films were fabricated by ex-situ solid phase crystallization (SPC) of amorphous films at the annealing temperature region of $900-1100^{\circ}C$ for 2 h in a pure oxygen atmosphere. The amorphous films were deposited on polycrystalline $BaZrO_3$ (poly-BZO) substrates by dc-magnetron sputtering at room temperature. The Curie temperatures ($T_C$) of all composite films were insignificantly altered in the range of 368-372 K. The highest LFMR value of 1.29 % in 0.5 kOe with the maximum dMR/dH value of $37.4%kOe^{-1}$ at 300 K was obtained from 900 nm-thick composite film annealed at $1100^{\circ}C$. The improved LFMR properties of the composite films are attributed to effective spin-dependent scattering at the $La_{0.7}Sr_{0.3}Mn_{1+d}O_3$ grain boundaries sharpened by adjacent chemically compatible $Mn_3O_4$ grains.

• 한국전기전자재료학회논문지
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• 제18권3호
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• pp.276-283
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• 2005

Magnetic tunneling transistor (MTT) device using the amorphous n-type Si semiconductor film for base and collector consisting of the [CoFe/NiFe](free layer) and Si(top layer) multilayers was used to study the spin-dependent hot electron magnetocurrent (MC) and tunneling magnetoresistance (TMR) at room temperature. A large MC of 40.2 % was observed at the emitter-base bias voltage ( $V_{EB}$ ) of 0.62 V. The increasing emitter hot current and transfer ratio ( $I_{C}$/ $I_{E}$) as $V_{EB}$ are mainly due to a rapid increase of the number of conduction band states in the Si collector. However, above the $V_{EB}$ of 0.62 V, the rapid decrease of MC was observed in amorphous Si-based MTT because of hot electron spin-dependent elastic scattering across CoFe/Si interfaces.