• Title/Summary/Keyword: magnetic oxide

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Fabrication and Magnetic Properties of Co Nanostructures in AAO Membranes

  • Jung, J.S.;Malkinski, L.;Lim, J.H.;Yu, M.;O'Connor, C.J.;Lee, H.O.;Kim, E.M.
    • Bulletin of the Korean Chemical Society
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    • v.29 no.4
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    • pp.758-760
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    • 2008
  • Nanoporous AAO (Anodic Aluminum Oxide) membranes have many advantages as a template for variety of magnetic materials. Materials can be embedded into the pores by electrodeposition, sputtering or magnetic-field-assisted infiltration of magnetic nanoparticles. This work focuses on the fabrication of the magnetic structures in the AAO templates by electrodeposition. Our method allows the controlled growth of Co nanostructures within the porous alumina membrane in the form of dots, rods and long wires. The shape of Co nanostructures has been investigated by field emission scanning electron microscope (FESEM). The magnetic hysteresis loops of Co nanostructures were measured using SQUID at 5 K and 300 K. The magnetic properties of the Co nanostructures are proportional to their aspect ratios and can be controlled by changing the aspect ratios.

Structural and Magnetic Properties of Dilute Spinel Ferrites: Neutron Diffractometry and Magnetometry Investigations

  • Mamiya, H.;Terada, N.;Kitazawa, H.;Hoshikawa, A.;Ishigaki, T.
    • Journal of Magnetics
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    • v.16 no.2
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    • pp.134-139
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    • 2011
  • Magnetic properties of highly zinc-substituted manganese ferrites are discussed on the basis of cation distribution. High throughput neutron powder diffractometry indicates that the prepared samples possess a nearly normal spinel structure, where the substitution of nonmagnetic zinc ions mainly causes the dilution of magnetic ions in the A-sublattice and consequently affects bond-randomness in the B-sublattice. On the other hand, the estimated occupancy of manganese ions in the B site indicates that random anisotropy effects due to local Jahn-Teller distortions gradually weaken with the substitution. Bulk magnetometry indicates that the substitution smears the transition from a paramagnetic phase to a soft-magnetic phase. Furthermore, at lower temperatures, such a soft-magnetic phase is destabilized and a magnetic glassy state appears. These features of the magnetic properties of dilute spinel ferrites are discussed from the viewpoint of the above-mentioned various types of disorders.

Molecular imaging application of iron oxide nanoradiomaterial

  • Ran Ji Yoo;Ji Yong Park;Tae Hyeon Choi;Jin Sil Kim;Yun-Sang Lee
    • Journal of Radiopharmaceuticals and Molecular Probes
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    • v.7 no.2
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    • pp.133-140
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    • 2021
  • Various iron oxide nanoparticle-based radiomaterials(IO-NRM) can be used for multimodal imaging of magnetic resonance imaging and molecular imaging, can be easily sized, can be easily functionalized, and have biocompatibility, making them a very good platform for molecular imaging. Based on the previously revealed molecular imaging technology of iron oxide nanoparticles, this paper introduces the in vivo distribution and use in various diseases through iron oxide nanoparticles-based radiolabeled compounds for diagnosis and treatment of iron oxide nanoparticles-based molecular imaging platforms. We would like to look forward to its potential as a radiopharmaceutical.

Magnetism of Ferric Iron Oxide and Its Significance in Martian Lithosphere (화성 암권의 진화해석을 위한 예비연구: 3가철 산화물의 자화특성)

  • Jeong, Doo-Hee;Yu, Yong-Jae
    • Journal of the Mineralogical Society of Korea
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    • v.24 no.3
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    • pp.189-194
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    • 2011
  • Martian satellite missions indicate that Martian equatorial plains are covered by ferric iron oxide. As a non-destructive technique, low-temperature treatment of remanent magnetization is effective in identifying magnetic minerals in rocks. In the present study, four sets of ferric iron oxides were prepared by aqueous alteration of ferrihydrite at warm conditions and four others by dehydration of goethite. As the amount of aluminous trivalent cations increases, crystallographic lattice parameters and N$\acute{e}$el temperatures decrease. Such declines originate from lattice distortion as the smaller aluminous trivalent cations substitue the larger terric irons. Whilst high remanence memory was observed for aqueously produced ferric iron oxide, low remanence memory was observed for dehydrated ferric iron oxide. In the future. magnetic remanence memory would be powerful in diagnosing the origin of ferric iron oxide.

Fluorescent Magnetic Silica Nanotubes with High Photostability Prepared by the Conventional Reverse Micro-Emulsion Method

  • Zhang, Yuhai;Son, Sang Jun
    • Bulletin of the Korean Chemical Society
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    • v.33 no.12
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    • pp.4165-4168
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    • 2012
  • Magnetic fluorescent silica nanotubes were fabricated using reverse micro-emulsions coupled with conventional sol-gel methods. Anodic aluminum oxide templates were used to separate spatially the magnetic and the fluorescent moieties on individual nanotubes and so prevent quenching of the fluorescence. C18 and fluorescent layers were deposited sequentially on silica. Magnetism was then obtained by the introduction of pre-made magnetic nanoparticles inside the nanotubes. The photo- and chemical stabilities of nanotubes were demonstrated through dye release and photobleaching tests. The produced nanotubes did not show fluorescence quenching upon the addition of the nanoparticles, an advantage over conventional spherical fluorescent magnetic nanoparticles. High photostability of nanotubes, magnetism and biocompatiblily make them potentially useful in bioanalysis.

MBE growth and magnetic properties of epitaxial FeMn2O4 film on MgO(100)

  • Duong, Van Thiet;Nguyen, Thi Minh Hai;Nguyen, Anh Phuong;Dang, Duc Dung;Duong, Anh Tuan;Nguyen, Van Quang;Cho, Sunglae
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.318.2-318.2
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    • 2016
  • FeM2X4 spinel structures, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics. Both the Fe and M ions can occupy tetrahedral and octahedral sites; therefore, these types of compounds can display various physical and chemical properties [1]. On the other hand, the electronic and magnetic properties of these spinel structures could be modified via the control of cation distribution [2, 3]. Among the spinel oxides, iron manganese oxide is one of promising materials for applications. FeMn2O4 shows inverse spinel structure above 390 K and ferrimagnetic properties below the temperature [4]. In this work, we report on the structural and magnetic properties of epitaxial FeMn2O4 thin film on MgO(100) substrate. The reflection high energy electron diffraction (RHEED) and X-ray diffraction (XRD) results indicated that films were epitaxially grown on MgO(100) without the impurity phases. The valance states of Fe and Mn in the FeMn2O4 film were carried out using x-ray photoelectron spectrometer (XPS). The magnetic properties were measured by vibrating sample magnetometer (VSM), indicating that the samples are ferromagnetic at room temperature. The structural detail and origin of magnetic ordering in FeMn2O4 will be discussed.

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Removal of Cu(II) ions by Alginate/Carbon Nanotube/Maghemite Composite Magnetic Beads

  • Jeon, Son-Yeo;Yun, Ju-Mi;Lee, Young-Seak;Kim, Hyung-Il
    • Carbon letters
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    • v.11 no.2
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    • pp.117-121
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    • 2010
  • The composites of alginate, carbon nanotube, and iron(III) oxide were prepared for the removal of heavy metal in aqueous pollutant. Both alginate and carbon nanotube were used as an adsorbent material and iron oxide was introduced for the easy recovery after removal of heavy metal to eliminate the secondary pollution. The morphology of composites was investigated by FE-SEM showing the carbon nanotubes coated with alginate and the iron oxide dispersed in the alginate matrix. The ferromagnetic properties of composites were shown by including iron(III) oxide additive. The copper ion removal was investigated with ICP AES. The copper ion removal efficiency increased greatly over 60% by using alginate-carbon nanotube composites.

Synthesis of Cobalt Oxide Film by Thermal Decomposition for Potential Various Applications

  • Han, Seong Ho;Park, Bo Keun;Son, Seong Uk;Kim, Chang Gyoun;Chung, Taek-Mo
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.365.1-365.1
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    • 2014
  • Cobalt oxide has excellent various properties such as high catalytic activity, antiferromagnetism, and electrochromism. So cobalt oxides offer a great potential for their applications in the various areas such as optical gas sensor, catalysts for oxidation reaction, electrochromic devices, high temperature solar selective absorbers, magnetic materials, pigment for glasses and ceramics, and negative electrodes for lithium-ion batteries. We have synthesized novel cobalt complexes by simple reaction of cobalt bistrimethylsilylamide as a starting material with a lot of conventional ligands as potential cobalt oxide precursors. The studies include the facile preparation, structural characterization, and spectroscopic analysis of the new precursors. We are making efforts to grow cobalt oxide thin films using cobalt complexes newly synthesized in this study using deposition techniques.

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SIMS glancing anlge을 적용한 tunnel oxide 내 Nitorgen 깊이 분해능 향상 연구

  • Lee, Jong-Pil;Choe, Geun-Yeong;Kim, Gyeong-Won;Kim, Ho-Jeong;Han, O-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.41-41
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    • 2011
  • Flash memory에서 tunnel oxide film은 electron tunnelling 현상을 이용하여 gate에 전하를 전달하는 통로로 사용되고 있다. 특히, tunnel oxide film 내부의 charge trap 현상과 불순물이 소자 특성에 직접적인 영향을 주고 있어, 후속 N2O/NO 열처리 공정에서 SiO2/Si 계면에 nitrogen을 주입하여 tunnel oxide film 특성을 개선하고 있다. 따라서 N2O/NO 열처리 공정 최적화를 위해서는 tunnel oxide film 내 N 농도와 분포에 대한 정확한 평가가 필수적이다[1]. 본 실험에서는 low energy magnetic SIMS를 이용하여 N2O로 열처리된 tunnel oxide film 내의 N농도를 보다 정확하게 평가하고자 하였다. 사용된 시료는 Si substrate에 oxidation 이후 N2O 열처리를 진행하여 tunnel oxide를 형성시켰으며, 분석 impact energy는 surface effect최소화와 최상의 depth resolution 확보를 위해 250eV를 사용하였으며, matrix effect와 mass interference를 방지하기 위해 MCs+ cluster mode[2]로 CsN signal를 검출하였다. 실험 결과, 특정 primary beam 입사각도에서 nitrogen depth resolution 저하 현상이 발생하였고, SIMS crater 표면이 매우 거칠게 나타났다. 이에, Depth resolution 저하 현상을 개선하기 위해 극한의 glancing 입사각 조건으로 secondary extraction voltage 변화를 통해 depth resolution이 개선되는 최적의 impact energy와 primary beam 입사각 조건을 확보하였다. 그 결과 nitrogen의 depth resolution은 1.6nm의 depth resolution을 확보하였으며, 보다 정확한 N 농도와 분포를 평가할 수 있게 되었다.

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Structural Characterization and Dielectric Studies of Superparamagnetic Iron Oxide Nanoparticles

  • Sivakumar, D.;Naidu, K. Chandra Babu;Nazeer, K. Prem;Rafi, M. Mohamed;kumar, G. Ramesh;Sathyaseelan, B.;Killivalavan, G.;Begam, A. Ayisha
    • Journal of the Korean Ceramic Society
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    • v.55 no.3
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    • pp.230-238
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    • 2018
  • Superparamagnetic iron oxide nanoparticles (SPIONs) have been prepared without using surfactants to assess their stability at different time intervals. The synthesized particles were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible-near infrared spectroscopy, and energy dispersive spectroscopy. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images of the samples were also investigated. The average particle size was measured to be 12.7 nm even in the polydispersed form. The magnetic and dielectric characteristics of the $Fe_3O_4$ nanoparticles have also been studied and discussed in detail.