• Title/Summary/Keyword: Trilayers

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Magnetization Reversal of Exchange-biased Bilayers and Trilayers Probed using Front and Back LT-MOKE

  • Kim, Ki-Yeon;Kim, Ji-Wan;Choi, Hyeok-Cheol;You, Chun-Yeol;Shin, Sung-Chul;Lee, Jeong-Soo
    • Journal of Magnetics
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    • v.14 no.1
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    • pp.36-41
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    • 2009

  • Magneto-optical Kerr effect (MOKE) magnetometry was used to investigate magnetization reversal dynamics in 30-nm NiFe/15-nm FeMn, 15-nm FeMn/30-nm CoFe bilayers, and 30-nm NiFe/(2,10)-nm FeMn/30-nm CoFe trilayers. The in-plane magnetization components of each ferromagnetic layer, both parallel and perpendicular to the applied field, were separately determined by measuring the longitudinal and transverse MOKE hysteresis loops from both the front and back sides of the film for an oblique incident s-polarized beam. The magnetization of the FeMn/CoFe bilayer was reversed abruptly and symmetrically through nucleation and domain wall propagation, while that of the NiFe/FeMn bilayer was reversed asymmetrically with a dominant rotation. In the NiFe/FeMn/CoFe trilayers, the magnetic reversal of the two ferromagnetic layers proceeded via nucleation and domain wall propagation for 2-nm FeMn, but via asymmetric rotation for 10-nm FeMn. The exchange-biased ferromagnetic layers showed the magnetization reversal along the same path in the film plane for the decreasing and increasing field branches from transverse MOKE hysteresis loops, which can be qualitatively explained by the theoretical model of the exchange-biased ferromagnetic/antiferromagnetic systems.

  • https://doi.org/10.4283/JMAG.2009.14.1.036 인용 PDF KSCI

Hysteresis Loops, Critical Fields and Energy Products for Exchange-spring Hard/soft/hard Trilayers

  • Chen, B.Z.;Yan, S.;Ju, Y.Z.;Zhao, G.P.;Zhang, X.C.;Yue, M.;Xia, J.
    • Journal of Magnetics
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    • v.20 no.1
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    • pp.31-39
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    • 2015

  • Macroscopic hysteresis loops and microscopic magnetic moment distributions have been determined by a three-dimensional (3D) model for exchange-coupled Sm-Co/${\alpha}-Fe$/Sm-Co trilayers with in-plane collinear easy axes. These results are carefully compared with the popular one-dimensional (1D) micromagnetic models and recent experimental data. It is found that the results obtained from the two methods match very well, especially for the remanence and coercivity, justifying the calculations. Both nucleation and coercive fields decrease monotonically as the soft layer thickness $L^s$ increases while the largest maximum energy product (roughly 50 MGOe) occurs when the thicknesses of hard and soft layers are 5 nm and 15 nm, respectively. Moreover, the calculated angular distributions in the thickness direction for the magnetic moments are similar. Nevertheless, the calculated nucleation and pinning fields as well as the energy products by 3D OOMMF are systematically smaller than those given by the 1D model, due mainly to the stray fields at the corners of the films. These demagnetization fields help the magnetic moments at the corners to deviate from the previous saturation state and facilitate the nucleation. Such an effect enhances as $L^s$ increases. When the thicknesses of hard and soft layers are 10 nm and 20 nm, respectively, the pinning field difference is as large as 30%, while the nucleation fields have opposite signs.

  • https://doi.org/10.4283/JMAG.2015.20.1.031 인용 PDF KSCI

A Study on the Magnetoresistive RAM (MRAM) Characteristics of NiFeCo/Cu/Co Trilayers (NiFeCo/Cu/Co 삼층막의 자기저항 메모리 특성에 관한 연구)

  • 김형준;이병일;주승기
    • Journal of the Korean Magnetics Society
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    • v.7 no.3
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    • pp.152-158
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    • 1997

  • NiFeCo/ Cu /Co trilayers were formed on 4$^{\circ}$ tilt-cut Si(111) substrates with a Cu(50$\AA$) underlayer and large-scaled test magnetoresistive RAM (MRAM) cells were fabricated using a conventional lithographic process. NiFeCo / Cu /Co trilayers deposited on the same templates without any applied magnetic field showed strong in plane uniaxial magnetic anisotropy and excellent magnetoresistive (MR) properties such as high MR ration and sensitivity within a low external magnetic field, which are suitable properties for a MRAM application. In order to obtain optimized MR results in NiFeCo /Cu /Co trilayers, the thickness of Cu spacer was varied. Interlayer coupling between two magnetic layers was observed and it was found that the MR properties were strongly dependent on the coupling force, especially near 20 $\AA$ of Cu spacer thickness. Test MRAM cells were fabricated using the optimized NiFeCo (60$\AA$)/ Cu (25$\AA$)/ Co (30$\AA$) trilayer thin films. With a 10 mA of sense current and 5$\times$$10^5$ of word current, 10 mV of signal output was obtained, which implies the strong potentials of NiFeCo/ Cu /Co trilayer thin films for a MRAM application.

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