• Title/Summary/Keyword: Ferromagnetic linewidth

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Angular Dependence of Ferromagnetic Resonance Linewidth in Exchange Coupled CoFe/MnIr Bilayers (교환 결합력을 갖는 CoFe/MnIr 박막에서 강자성 공명 선폭의 각도 의존성 연구)

  • Yoon, Seok Soo;Kim, Dong Young
    • Journal of the Korean Magnetics Society
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    • v.26 no.2
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    • pp.50-54
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    • 2016
  • We analyzed the angular dependence of ferromagnetic resonance linewidth in exchange coupled CoFe/MnIr bilayers. The maximum and minimum linewidth was observed in the easy and hard direction of unidirectional anisotropy by exchange coupling, respectively, and it was well agreed with the angular dependence of exchange bias field. The maximum linewidth was due to the twist of CoFe magnetization near CoFe/MnIr interface from direction of pinned MnIr spin to direction of applied magnetic field. While, minimum linewidth more higher than that of CoFe was related to rotatable anisotropy field, and explained by easy axis distribution of MnIr grains.

Magnetic Properties of La-doped YIG Films Prepared by LPE(Liquid Phase Epitaxy) (LPE 성장법으로 성장시킨 La을 첨가한 YIG 막의 자성특성)

  • 김동영;한진우;김명수;이상석
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.3
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    • pp.257-262
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    • 2001
  • Single crystalline films of La doped YIG(yttrium iron garnet) were grown by the liquid phase epitaxy. The lattice constants of films obtained by DCD(double crystalline diffractometer) measurement increased with increasing La contents in films. In particular, lattice constants of films grown wiht Y/La=20 solution were nearly same as those of GGG (gadolinium gallium garnet) substrate. The saturation magnetization measured with VSM (vibrating sample magnetometer) was about 1750Gauss which is the same as that of pure YIG irrespective of La contents in films. FMR(ferromagnetic resonance) linewidth of La doped YIG was smaller than that of pure YIG. Since appropriate La doping decreases the lattice mismatch between film and substrate, the FMR linewidth was Y/La=20 in this experiment.

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Size Dependence of FMR Linewidth in Iron Oxide Nanoparticles (산화철 나노입자의 크기에 따른 강자성 공명 신호의 선폭 특성)

  • Kim, Dong Young;Yoon, Seok Soo
    • Journal of the Korean Magnetics Society
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    • v.24 no.1
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    • pp.11-17
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    • 2014
  • We measured the ferromagnetic resonance (FMR) signal using the monodisperse iron oxide nanoparticles with size D=4.67 nm, 5.64 nm and 6.34 nm synthesized by using the thermal decomposition method, respectively. The measured ferromagnetic resonance signals were compared with the calculated ones for superparamagnetic nanoparticles with lognormal volume distribution. The FMR linewidth broadening was propositional to tanh($V^2$), where V was volume of nanoparticles. The narrow linewidth of small size nanoparticles was due to the surface spins, while the broad linewidth of large size nanoparticles was due to the bulk spins affected by the crystalline structure of iron oxide nanoparticles. The superposition of surface and bulk effect was confirmed at D=5.64 nm nanoparticles, which was near the critical size for linewidth transition from surface effect to bulk effect.

Rotatable Anisotropy Field in Exchange Coupled CoFe/MnIr(2.5 nm) Thin Films (교환 결합력을 갖는 CoFe/MnIr(2.5 nm) 박막의 회전 이방성 자기장 특성)

  • Yoon, Seok Soo;Kim, Dong Young
    • Journal of the Korean Magnetics Society
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    • v.27 no.3
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    • pp.77-81
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    • 2017
  • The rotatable anisotropy effect was observed in the ferromagnetic resonance measurement in exchange coupled ferromagnetic/antiferromagnetic thin films and it was due to rotation of antiferromagnetic layer by the exchange coupling energy. We analyzed the CoFe thickness dependence of rotatable anisotropy field and ferromagnetic resonance linewidth in exchange coupled $CoFe(t_F)/MnIr(2.5nm)$ thin films. The rotatable anisotropy field was inversely propositional to the CoFe thickness and it was well fitted by the rotatable anisotropy energy of $0.96erg/cm^2$. The ferromagnetic resonance linewidth were linearly propositional to the rotatable anisotropy field in $t_F$ < 50 nm, while it was more dominated by the eddy current effect in $t_F$ > 50 nm.

Analysis of Ferromagnetic Resonance Linewidth in Ni Thin Film Fabricated by Electrodeposition Method (전기 도금법으로 제작한 Ni 박막의 강자성 공명 선폭 분석)

  • Kim, Dong Young;Yoon, Seok Soo
    • Journal of the Korean Magnetics Society
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    • v.24 no.2
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    • pp.60-65
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    • 2014
  • We obtained resonance field ($H_{res}$) and linewidth (${\Delta}H_{PP}$) from measured ferromagnetic resonance signal in the functions of polar angle (${\Theta}_H$) in Ni thin film of 240 nm thickness fabricated by electrodeposition method. The angular dependence of $H_{res}$ was well fitted with the calculated ones. We confirmed that the g-factor and effective demagnetization field were 2.18 and 445 emu/cc by the theoretical analysis of the resonance field, respectively. The angular dependence of ${\Delta}H_{PP}$ showed very large values at in-plane direction (${\Theta}_H=90^{\circ}$), which could not explained by the homogenous linewidth due to the Gilbert damping and inhomogeneous linewidth due to the angular variations and magnetization variations by the surface layer. Therefore, we considered the spin wave scattering (two magnon scattering) process in order to analyze the measured inhomogeneous linewidth, which was appeared in thicker film than the critical thickness of 50 nm. The defect medicated spin wave scattering played a key role in the electrodoposited Ni thin film of 240 nm thickness.

The study on effects of porosity grain size, magnetization and anisotropy field on the properties of ferromagnetic resonance (다결정 Mg-페라이트의 기공율, 입경, 포화 자화 및 이방성 자기장이 강자성 공명 특성에 미치는 영향 연구)

  • 김진호;주승기;최덕균
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.1
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    • pp.97-102
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    • 1995
  • The ferromagnetic resonance properties of Mg ferrites which have various porosity grain size, and saturation magnetization are measured at one frequency. This allows a determination of the anisotropy field(Ha). The saturation magnetization multiplied by porosity is the resonance magnetic field. As the saturation magnetization increases, the linewidth decerases due to decrement of magnetic inhomogenity in sample. the porosity is a major factor broadening the linewidth for Mg ferrite when porosity is more thatn 6%, and the anisotropy field is dominant when porosity is less than 6%.

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Ferromagnetic Resonance Observation of Martensitic Phase Transformation in Ni-Mn-Ga Ferromagnetic Shape Memory Films

  • Dubowik, J.;Kudryavtsev, Y.V.;Lee, Y.P
    • Journal of Magnetics
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    • v.9 no.2
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    • pp.37-39
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    • 2004
  • Polycrystalline Ni-Mn-Ga films have been deposited onto mica substrates held at 720 K by flash-evaporation method. At room temperature the films have a tetragonal structure with a = b = 0.598 and c = 0.576 nm typical for bulk $Ni_2MnGa$ below a martensitic transformation. Temperature measurements of ferromagnetic resonance reveal a martensitic phase transformation at 310 K. The transformation brings about a substantial decrease in the effective magnetization and a drastic increase in the ferromagnetic resonance linewidth due to a strong increase in the magnetic anisotropy in the martensitic phase.

Ferromagnetic resonance of Hensler $Ni_2$MnGa thin films

  • M. D. Huang;Lee, N. N.;Lee, Y. P.;J. Y. Rhee;J. Dubowik
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.116-119
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    • 2003
  • $Ni_2$MnGa films, deposited on mica and glass substrates, were studied by ferromagnetic resonance (FMR) technology. The temperature-dependent resonance field was measured and a martensitic phase transformation (MT) was found between 310 and 340 K, exhibiting an abnormality on the curve. The easy axis is found to be in the film plane. The line width increases as a whole with decreasing temperature, which is discussed in terms of the motional narrowing mechanism. The resonance field was also measured as a function of orientation and the results were fitted, exhibiting a good consistence.

Thermal Annealing Effect on Ferromagnetic Resonance Properties in CoFeB/MgO Thin Film (CoFeB/MgO 박막 재료의 열처리에 따른 강자성공명 특성)

  • Yoon, Seok-Soo;Kim, Dong-Young
    • Journal of the Korean Magnetics Society
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    • v.21 no.1
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    • pp.10-14
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    • 2011
  • We have measured the ferromagnetic resonance (FMR) signal in as deposited and $400^{\circ}C$ annealed CoFeB/MgO thin film to investigate the annealing effect on magnetic anisotropies and FMR linewidth (${\Delta}H_{PP}$). The uniaxial anisotropy field ($H_{K1}$) was only observed in the as deposited sample. Whereas, in the $400^{\circ}C$ annealed sample, the biaxial anisotropy field ($H_{K2}$) was additionally observed in accompany with uniaxial anisotropy field ($H_{K1}$). The appearance of biaxial anisotropy fields was originated from the crystalline growth of bcc CoFeB(001) from the MgO(001) interface and by the B diffusion during thermal annealing. Also, the ${\Delta}H_{PP}$ of $400^{\circ}C$ annealed sample was increased compared with that of as deposited sample, which was due to the broad distribution of the magnetization axis by the biaxial anisotropy.

A study on the properties of microwave loss of ferrite with various Fe contents in $Mn_{0.05}Mg_{11.9-2x}Fe_{4x}O_{4+r}+2wt%$Al_{2}O_{3}$ ($Mn_{0.05}Mg_{11.9-2x}Fe_{4x}O_{4+r}$+2wt%$Al_{2}O_{3}$ 조성내 Fe량 변화에 따른 마이크로파 손실 특성 연구)

  • 김성재;정명덕
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.6
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    • pp.143-148
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    • 1994
  • In order to study the effect of D.C resistivity of sample on electromagnetic loss of ferrite at microwave frequency, samples were prepared for having differences in resistivity of an order of two. Microwave permeability($\mu$), permitivity($\varepsilon$) and effective linewidth(${\Delta}H_{eff}$), and ferromagnetic resonance linewidth(${\Delta}$H) were characterized. Tan${\delta}{\mu}$, tan${\delta}{\varepsilon}$ and ${\Delta}H_{eff}$ were decreased with increasing the resistivity and (${\Delta}$H) was increased with increasing Fe concentration, which was due to an increase of anisotropy magnetic field (=Ha).

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