• Title/Summary/Keyword: 강자성공명

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A Study on the Ferromagnetic Resonance of FeNb Thin Films (FeNb 박막의 강자성 공명 연구)

  • Lim, Woo-Young;Baek, Jong-Sung;Lee, Soo-Hyung
    • Journal of the Korean Magnetics Society
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    • v.14 no.4
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    • pp.120-126
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    • 2004
  • In order to understand the temperature dependence of magnetic properties of $F_{84}Nb_{16}$(wt.%) thin films, ferromagnetic resonance experiments have been carried out. The ferromagnetic resonance spectra for all temperatures consist of several volume modes and one (or two) surface modes. It is suggested that both surface of the film have a perpendicular hard axis to the film plane (negative surface magnetic anisotropy). Saturation magnetization coincides with the Block's T$\^$2/3/ and spectroscopic splitting factor is almost constant in the temperature range from 113 K to 293 K. The surface magnetic anisotropy constant K$\_$s2/ of the film-substrate interface increased with decreasing temperature in the temperature range from 233 K to 293 K. The surface magnetic anisotropy constant K$\_$s1/ of the air-substrate interface decreased from -0.322 erg/$\textrm{cm}^2$ to -0.394 erg/$\textrm{cm}^2$ as the temperature decreased to 253 K and was almost constant below 233 K.233 K.

Exchange Coupling Effect on Microwave Permeability in CoFe/MnIr Bilayers (교환 결합력을 갖는 CoFe/MnIr 박막의 마이크로파 투자율 특성)

  • Kim, Dong-Young;Kim, Chong-Oh;Kim, Cheol-Gi;Tsunoda, M.;Takahashi, M.
    • Journal of the Korean Magnetics Society
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    • v.16 no.5
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    • pp.234-239
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    • 2006
  • We measured the microwave permeability in the frequency range of 100 MHz$\sim$9 GHz in the exchange biased CoFe/MnIr films. The results were analyzed based on the Landau-Lifshitz-Gilbert theory. The initial permeability and ferromagnetic resonance frequency was tuned by controlling the CoFe thickness and unidirectional anisotropy. The tunable range of ferromagnetic resonance frequency was up to 20 GHz in the thin CoFe layer of 1.5 nm. The CoFe/MnIr films showed the high permeability and low loss properties in the microwave frequency range. Thus, this material could be applied to the microwave devices.

Synthesis of Monodisperse Iron-oxide Nanoparticles from Fe(acac)3 Precursor (Fe(acac)3 전구체를 사용한 균일한 산화철 나노입자 제조)

  • Kim, Dong Young
    • Journal of the Korean Magnetics Society
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    • v.24 no.1
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    • pp.18-21
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    • 2014
  • The microwave absorption ($P_{tot}$), which is the double integration value of ferromagnetic resonance signal, propositional to the saturation magnetization, and the increase of the $P_{tot}$ measured during the thermal reaction time expect the growth process of the nanoparticles. Therefore, in this work, we measured the $P_{tot}$ in order to obtain the growth time of iron oxide nanoparticles after thermal decomposition of $Fe(acac)_3$ precursor at aging temperature $T_a=273$, 300 and $324^{\circ}C$, respectively. The best condition for monodisperse nanoparticles was obtained at $T_a=300^{\circ}C$, which condition showed the most rapid increase of $P_{tot}$ with thermal reaction time. Finally, the rapid growth rate was necessary condition for the synthesis of iron-oxide monodisperse nanoparticles.