• Title, Summary, Keyword: Ferromagnetic resonance

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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 Frequency of Patterned Synthetic Antiferromagnet

  • Gong, Yo-Chan;Im, Sang-Ho;Lee, Gyeong-Jin
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.57-58
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    • 2008
  • 외부 자기장이 spin-flip field보다 작은 조건 하에서 마이크로 사이즈로 패턴된 synthetic antiferromanet의 ferromagnetic resonance frequency를 표현할 수 있는 이론식을 유도했다. 또한 유도된 이론식을 통해 synthetic antiferromagnet의 기하학적, 자기적 성질이 ferromagnetic resonance frequency가 미치는 영향에 대해 연구했다.

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Derivation of dc Voltages in a Magnetic Multilayer Undergoing Ferromagnetic Resonance

  • Oh, Dong-Keun;Lee, Cheol-Eui
    • Journal of Magnetics
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    • v.10 no.3
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    • pp.77-79
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    • 2005
  • In this work, we present a comprehensive and systematic approach for the derivation of the dc voltage generated by a magnetic multilayer undergoing ferromagnetic resonance, originally derived by Berger. Our alternative derivation applies especially in the limit of the spin diffusion length much longer than the carrier mean free path.

Electron Paramagnetic Resonance Study of Al-incorporated ZnO:Mn Diluted Magnetic Semiconductors

  • Park, Jun Kue;Lee, K.W.;Choi, D.M.;Lee, Cheol Eui
    • Journal of the Korean Physical Society
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    • v.73 no.12
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    • pp.1884-1888
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    • 2018
  • We have employed electron paramagnetic resonance spectroscopy and magnetization measurements in order to study the effect of Al-incorporation on the magnetic interactions in ZnO:Mn diluted magnetic semiconductors. Al-doping is shown to decrease the antiferromagnetic correlation and to increase the ferromagnetic interaction, which is attributed to the hydrogen-mediated ferromagnetic Mn complexes in our Mn-doped ZnO samples.

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.

Effects of Microstructure on the Magnetic Properties of Mg-ferrite Sintered Body (미세 구조가 Mg-페라이트 소결체의 자성에 미치는 영향)

  • 김성재;정명득;백종규
    • Journal of the Korean Ceramic Society
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    • v.32 no.4
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    • pp.436-440
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    • 1995
  • Effects of microstructure of two Mg-ferrite specimens with the same starting composition and relative density but with different grain size on B-H hysteresis loop, natural resonance frequency, and ferromagnetic resonance line width are reported. Such properties as B-H hysteresis loop, saturation magnetization, natural resonance frequency, and ferromagnetic resonance line width were influenced by the microstructure development during sintering. Large grain size specimen showed high saturation magnetization, low coercive force, low natural resonance frequency, and low ferromagnetic resonance line width compared with the specimen of small grain size. The main reason for the changes in properties can be explained by the variation in anisotropic characteristics due to Fe+2 content generated during sintering process.

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Analysis of Ferromagnetic and Spin Wave Resonance Signals in CoFeB Thin Films (CoFeB 박막 재료에서 강자성 및 스핀파 공명 신호 분석)

  • Kim, Dong Young;Yoon, Seok Soo
    • Journal of the Korean Magnetics Society
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    • v.24 no.6
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    • pp.165-170
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    • 2014
  • We analyzed the ferromagnetic and spin wave resonance signals measured in amorphous CoFeB thin films with different thickness. The ferromagnetic resonance field ($H_{FMR}$) was not depend on the thickness of CoFeB films, but the spin wave resonance field ($H_{SWR}$) was well fitted with the theoretical prediction depending on the thickness. The uniaxial anisotropy field of $H_k$ = 37 Oe was obtained from the angular dependent $H_{FMR}$ in CoFeB films. The $H_{SWR}$ showed same angular behaviors with $H_{FMR}$, however, the amplitude of spin wave resonance signals showed 5.7 times higher than that of ferromagnetic resonance signals in CoFeB film with t = 100 nm. The higher signals were due to the two reasons; one was the small damping for the spin wave propagation without degradation, the other was uniform magnetization for the ideal standing wave modes.

Ferromagnetic Resonance and X-Ray Reflectivity Studies of Pulsed DC Magnetron Sputtered NiFe/IrMn/CoFe Exchange Bias

  • Oksuzoglu, Ramis Mustafa;Akman, Ozlem;Yildirim, Mustafa;Aktas, Bekir
    • Journal of Magnetics
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    • v.17 no.4
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    • pp.245-250
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    • 2012
  • Ferromagnetic resonance and X-ray specular reflectivity measurements were performed on $Ni_{81}Fe_{19}/Ir_{20}Mn_{80}/Co_{90}Fe_{10}$ exchange bias trilayers, which were grown using the pulsed-DC magnetron sputtering technique on Si(100)/$SiO_2$(1000 nm) substrates, to investigate the evolution of the interface roughness and exchange bias and their dependence on the NiFe layer thickness. The interface roughness values of the samples decrease with increasing NiFe thickness. The in-plane ferromagnetic resonance measurements indicate that the exchange bias field and the peak-to-peak line widths of the resonance curves are inversely proportional to the NiFe thickness. Furthermore, both the exchange bias field and the interface roughness show almost the same dependence on the NiFe layer thickness. The out-of plane angular dependent measurements indicate that the exchange bias arises predominantly from a variation of exchange anisotropy due to changes in interfacial structure. The correlation between the exchange bias and the interface roughness is discussed.

Nano-Granular Co-Fe-AI-O Soft Ferromagnetic Thin Films for GHz Magnetic Device Applications

  • Sohn, Jae-Cheon;Byun, Dong-Jin
    • Journal of the Korean Ceramic Society
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    • v.43 no.3
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    • pp.143-147
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    • 2006
  • Co-Fe-Al-O nanogranular thin films were fabricated by RF-magnetron sputtering under an $Ar+O_2$ atmosphere. High resolution transmission electron microscopy revealed that the Co-Fe-Al-O films are composed of bcc (Co, Fe) nanograins finer than 5 nm and an Al-O amorphous phase. A very large electrical resistivity of $374{\mu}{\Omega}cm$ was obtained, together with a large uniaxial anisotropy field of 50 Oe, a hard axis coercivity of 1.25 Oe, and a saturation magnetization of 12.9 kG. The actual part of the relative permeability was measured to be 260 at low frequencies and this value was maintained up to 1.3 GHz. The ferromagnetic resonance frequency was 2.24 GHz. The resulting Co-Fe-Al-O nanogranular thin films with a high electrical resistivity and high resonance frequency are considered to be suitable for GHz magnetic device applications.

Magnetic Characteristics of YIG ferrites with Sintering Temperature (소결온도에 따른 YIG 페라이트의 자기적 특성)

  • 양승진;윤종남;최우석;김정식
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.1
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    • pp.65-69
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    • 2003
  • Microstructural and electromagnetic properties of YIG ferrites, (Y, Ca)-(Fe, V, In, Al)-O for Isolator/Circulator were investigated with the sintering temperature. YIG ferrites of $Y_{2.1}Ca_{0.9}Fe_{4.4}V_{0.5}In_{0.05}Al_{0.05}O_{12}$ were fabricated by sintering at $1300^{\circ}C$, $1330^{\circ}C$, $1350^{\circ}C$, $1370^{\circ}C$. Crystallographic and microstructural properties were measured using XRD and SEM. Saturation magnetization$(4{\pi}M_s)$ were measured using VSM, and FMR(Ferromagnetic Resonance) experiment was conducted to measure ferromagnetic resonance line width$({\Delta}H)$. Microwave characteristics of YIG ferrites were measured using a Network Analyzer. The YIG ferrite of $Y_{2.1}Ca_{0.9}Fe_{4.4}V_{0.5}In_{0.05}Al_{0.05}O_{12}$, sintered at $1350^{\circ}C$, showed higher density, saturation magnetization and lower ferromagnetic resonance line width than those sintered at any other temperature.

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