• Title/Summary/Keyword: 강자성공명

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Microwave Absorbing Properties of M-type Barium Ferrites with BaTi0.5Co0.5Fe11O19 Composition in Ka-band Frequencies (BaTi0.5Co0.5Fe11O19 조성을 갖는 M형 바륨 페라이트의 Ka-밴드 전파흡수특성)

  • Kim, Yong-Jin;Kim, Sung-Soo
    • Journal of the Korean Magnetics Society
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    • v.19 no.6
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    • pp.203-208
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    • 2009
  • Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.

Mössbauer Study on Crystallographic and Magnetic Properties of Mechanical Alloying Fe-M(M=Cr, Mn, Cu, Zn) Powders (기계적 합금화한 Fe계 분말 특성에 관한 뫼스바우어 분광학적 연구)

  • Park, Jae-Yoon;Choi, Jae-Joo
    • Journal of the Korean Magnetics Society
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    • v.17 no.1
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    • pp.26-29
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    • 2007
  • Fe-based powders, Fe-M(M=Cr, Mn, Cu, Zn), were prepared in Ar gas by mechanical alloying and their crystallographic and magnetic properties were investigated. X-ray diffraction indicates that the cubic lattice parameter increases for the M substitution. The distance of closest approach around M can explained the increase of lattice constant in Fe-M powders. $M\"{o}ssbauer$ spectroscopy measurements on Fe-M samples indicates the coexistence of ferromagnetic phases and paramagnetic phase that are created by the distribution of local environment M on Fe atom. On the other hand, The spread of line-width on $M\"{o}ssbauer$ spectra can be explained by the distribution of hyperfine magnetic fields. The results of quadrupole shift and isomer shift revealed that M substitutions in Fe-M powders didn't change both structure and the local charge distribution around Fe atom severely.

Annealing Effect of Surface Magnetic Properties in CoTi Thin Films (열처리 효과가 CoTi계 박막의 표면자기특성에 미치는 영향)

  • 김약연;백종성;이성재;임우영;이수형
    • Journal of the Korean Magnetics Society
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    • v.7 no.1
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    • pp.38-43
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    • 1997
  • For amorphous $Co_{1-x}Ti_x$(X=0.13, 0.16, 0.21 at.%) thin films deposited by DC magnetron sputtering method ferromagnetic resonance experiments have been used to investigate the dependence of surface magnetic properties according to annealing temperature (150~225 $^{\circ}C$). Spin wave resonance spectra for all annealing temperatures consist of several volume modes and one(or two) surface mode. It is suggested that both surfaces of the film have a perpendicular hard axis to the film plane(negative surface anisotropy). Also, the surface anisotropy $K_{s2}$ at substrate film interface is varied slowly from -0.11 to -0.25 erg/ $\textrm{cm}^2$ and the surface anisotropy $K_{s1}$ at film-air interface is varied from 0.16 to -0.53 erg/ $\textrm{cm}^2$ with increasing annealing temperature. We conjecture that the variation of surface anisotropy $K_{s1}$ is due to the increase of Co concentration resulted from Ti oxidation for low temperature annealing(150~200 $^{\circ}C$) and the diffusion of Co atoms near the film surfaces for high temperature annealing(225~250 $^{\circ}C$).

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Guidelines of IRPA/ICNIRP for Non-ionizing Radiation (비이온화방사선에 대한 IRPA/ICNIRP의 제반지침)

  • Lee, Soo-Yong
    • Journal of Radiation Protection and Research
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    • v.20 no.3
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    • pp.143-154
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    • 1995
  • In recent years, the development of new technologies using static magnetic fields has increased the possibility of human exposure to these fields and raised some concern as to their possible health effects. In several countries, governmental or other competent authorities have issued exposure limits that are mainly intended for specific uses, i.e., magnetic resonance imaging (MRI) and particle accelerators for high-energy Physics. Since applications of magnetic fields in industry and medicine are likely to grow in the future, thus increasing the possibility of occupational and general public exposure, and since the number of people with ferromagnetic implants and implanted electronic devices that can be affected by the fields is growing, there is a need for international guidelines. In the present papers, guidelines on limits of exposure to static magnetic fields are selected and discussed in order to review the guidelines of the International Non-ionizing Radiation Committee of the International Radiation Protection Association (IRPA/INIRC) for non-ionizing radiation(NIR)

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Effect of the Annealing Conditions on the Ferromagnetic Resonance of YIG Thin Film Prepared on GGG Substrate (Gd3Ga5O12 기판위에 성장된 Y3Fe5O12 박막의 열처리 조건에 따른 강자성 공명 특성 연구)

  • Lee, Yelim;Phuoc, Cao Van;Park, Seung-Young;Jeong, Jong-Ryul
    • Korean Journal of Materials Research
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    • v.25 no.12
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    • pp.703-707
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    • 2015
  • In this study, we investigated the effect of annealing conditions on the ferromagnetic resonance(FMR) of yttrium iron garnet ($Y_3Fe_5O_{12}$, YIG) thin film prepared on gadolinium gallium garnet ($Gd_3Ga_5O_{12}$, GGG) substrate. The YIG thin films were grown by rf magnetron sputtering at room temperature and were annealed at various temperatures from 700 to $1000^{\circ}C$. FMR characteristics of the YIG thin films were investigated with a coplanar waveguide FMR measurement system in a frequency range from 5 to 20 GHz. X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) were used to characterize the phase formation, crystal structure and composition of the YIG thin films. Field dependent magnetization curves at room temperature were obtained by using a vibrating sample magnetometer(VSM). The FMR measurements revealed that the resonance magnetic field was highly dependent on the annealing condition: the lowest FMR linewidth can be observed for the $800^{\circ}C$ annealed sample, which agrees with the VSM results. We also found that the Fe and O composition changes during the annealing process play important roles in the observed magnetic properties.

Magnetic Properties of Nanocrystalline Fe-Co-Cu-Nb-Si-B Alloys (Fe-Co-Cu-Nb-Si-B 초미세결정합금의 자기적 특성연구)

  • 김약연;백종성;서영수;임우영;유성초;이수형
    • Journal of the Korean Magnetics Society
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    • v.3 no.2
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    • pp.130-134
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    • 1993
  • The magnetic properties of the amorphous $Fe_{73.5-X}Co_{X}Cu_{1}Nb_{3}Si_{13.5}B_{9}(x=2,\;4)$ alloys, fabricated by a single roll rapid quenching technique and annealed at $400~650^{\circ}C$, have been investigated. The optimum annealing temperature is $550^{\circ}C$ for the amorphous $Fe_{71.5}Co_{2}Cu_{1}Nb_{3}Si_{13.5}B_{9}$ alloy. The properties of the nanocrystalline $Fe_{71.5}Co_{2}Cu_{1}Nb_{3}Si_{13.5}B_{9}$ alloy show the relative permeability of $1.1{\times}10^{4}$ and the coercive force of 0.22 Oe at 1 kHz. When annealed at $600^{\circ}C$, the nanocrystalline $Fe_{69.5}Co_{4}Cu_{1}Nb_{3}Si_{13.5)B_{9}$ alloy shows the relative permeability of $1.0{\times}10^{4}$ and the coercive force of 0.19 Oe at 1 kHz. From the X-ray measurement, it is found that the remarkably improved soft magnetic properties are the effect of the formation of $\alpha$-Fe(Si) grain. By the results of FMR exper-imeIlt, the optimum annealing condition is just below temperature which the peak-to-peak line width of FMR spectrum increase rapidly.

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Chemical Composition, Microstructure and Magnetic Characteristics of Cerium Substituted Yttrium Iron Garnet Thin Films Prepared by RF Magnetron Sputter Techniques (고주파 마그네트론 스퍼터 기법으로 제조된 Ce:YIG 박막의 화학 조성, 미세구조 및 자기적 특성)

  • 박명범;조남희
    • Journal of the Korean Magnetics Society
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    • v.10 no.3
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    • pp.123-132
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    • 2000
  • Cerium substituted YIG thin films were grown by rf magnetron sputter techniques. We investigated the effects of post-deposition heat-treatment as well as various deposition parameters such as substrate materials, substrate temperature. sputter power, and sputter gas types on the crystallinity, chemical composition, microstructure and magnetic characteristics of the films. Post-deposition heat treatment over 750 $\^{C}$ was applied to crystallize as-prepared amorphous films, and a strong tendency of particular crystallographic planes tying parallel to substrate surface was observed for the post-deposition heat-treated films on GGG substrate. The chemical composition of the films exhibited a wide range of chemical stoichiometry depending on the oxygen fraction of sputter gas, and in particular the composition of the film deposited in sputter gas with an oxygen fraction of R = 10% was Ce$\_$0.23/Y$\_$1.30/Fe$\_$3.50/O$\_$12/. With raising the temperature of post-deposition heat-treatment from 900 $\^{C}$ to 1100 $\^{C}$, the surface roughness of the film on GGG substrates increased from about 3 nm to 40 nm, but their coercive force and ferromagnetic resonance line width decreased from 0.477 kA/m to 0.369 kA/m and from 12.5 kA/m to 8.36 kA/m, respectively.

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Electromagnetic wave absorption characteristics in Ni-Mn-Zn Ferrite with varying Mn content and applied magnetic field (Ni-Mn-Zn ferrite의 합성과 Mn의 치환량 및 인가자장에 따른 전자기파 흡수 특성 연구)

  • Ji-Hye Lee;Sang-Min Lee;Young-Min Kang
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.33 no.6
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    • pp.294-302
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    • 2023
  • Ni-Mn-Zn ferrite, Ni0.5-xMnxZn0.5Fe2O4 (0 ≤ x ≤ 0.5), was synthesized using the sol-gel method to investigate the crystal structure, microstructure, magnetic properties, high-frequency characteristics, and electromagnetic (EM) wave absorption characteristics as a function of Mn substitution. As the Mn content increased, a continuous decrease in saturation magnetization (MS) was observed with little change in coercivity (HC). Samples for each composition (x) exhibited strong EM wave absorption performance with first and second strong EM wave absorption regions satisfying minimum reflection loss, RLmin < -40 dB in the 1.5~2.5, 6~11 GHz range, respectively. The EM wave absorption in Ni-Mn-Zn ferrite depends on magnetic loss, and adjusting µ' and µ'' spectra by Mn substitution or H field allows control of the EM wave absorption frequency.