Magnetization switching behavior of exchange-coupled bilayer nanodots characterized by magneto-optical Kerr effect

W. Zhou; T. Seki; K. Takanashi

doi:10.1063/1.4985848

Magnetization switching behavior of exchange-coupled bilayer nanodots characterized by magneto-optical Kerr effect

W. Zhou, T. Seki, K. Takanashi

Materials Development Division

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

Abstract

We investigated the magnetization switching behavior of exchange-coupled bilayer nanodots consisting of a soft magnetic Ni₈₁Fe₁₉ (permalloy; Py) layer and a perpendicularly magnetized L1₀-FePt layer by measuring the polar magneto-optical Kerr effect (MOKE). A MOKE system having a 2-μm-diameter laser spot was used, which detected the signal from around 20 nanodots of 200 nm in diameter. The measured polar MOKE loops exhibited a two-step behavior attributable to each magnetization reversal process of the Py and L1₀-FePt layers, allowing us to evaluate the switching field (Hsw) of L1₀-FePt from the MOKE loop. Under the application of both a static magnetic field and an rf magnetic field (hrf), the nanodots showed a clear Hsw reduction with characteristic hrf frequency dependence. This Hsw reduction is well interpreted as a behavior of spin wave-assisted magnetization switching. We also discuss the influence of the Py layer thickness on spin wave-assisted Hsw reduction.

Original language	English
Article number	093902
Journal	Journal of Applied Physics
Volume	122
Issue number	9
DOIs	https://doi.org/10.1063/1.4985848
Publication status	Published - 2017 Sept 7

ASJC Scopus subject areas

Physics and Astronomy(all)

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title = "Magnetization switching behavior of exchange-coupled bilayer nanodots characterized by magneto-optical Kerr effect",

abstract = "We investigated the magnetization switching behavior of exchange-coupled bilayer nanodots consisting of a soft magnetic Ni81Fe19 (permalloy; Py) layer and a perpendicularly magnetized L10-FePt layer by measuring the polar magneto-optical Kerr effect (MOKE). A MOKE system having a 2-μm-diameter laser spot was used, which detected the signal from around 20 nanodots of 200 nm in diameter. The measured polar MOKE loops exhibited a two-step behavior attributable to each magnetization reversal process of the Py and L10-FePt layers, allowing us to evaluate the switching field (Hsw) of L10-FePt from the MOKE loop. Under the application of both a static magnetic field and an rf magnetic field (hrf), the nanodots showed a clear Hsw reduction with characteristic hrf frequency dependence. This Hsw reduction is well interpreted as a behavior of spin wave-assisted magnetization switching. We also discuss the influence of the Py layer thickness on spin wave-assisted Hsw reduction.",

author = "W. Zhou and T. Seki and K. Takanashi",

note = "Funding Information: This work was supported by the Grant-in-Aid for Scientific Research B (16H04487), the PRESTO “Innovative Nano-electronics through Interdisciplinary Collaboration among Material, Device and System Layers” (JPMJPR1422), and the Research Grant from the TEPCO Memorial Foundation. The device fabrication and the structural characterization were partly performed at the Cooperative Research and Development Center for Advanced Materials, IMR, Tohoku University. Publisher Copyright: {\textcopyright} 2017 Author(s).",

year = "2017",

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doi = "10.1063/1.4985848",

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AU - Zhou, W.

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N1 - Funding Information: This work was supported by the Grant-in-Aid for Scientific Research B (16H04487), the PRESTO “Innovative Nano-electronics through Interdisciplinary Collaboration among Material, Device and System Layers” (JPMJPR1422), and the Research Grant from the TEPCO Memorial Foundation. The device fabrication and the structural characterization were partly performed at the Cooperative Research and Development Center for Advanced Materials, IMR, Tohoku University. Publisher Copyright: © 2017 Author(s).

PY - 2017/9/7

Y1 - 2017/9/7

N2 - We investigated the magnetization switching behavior of exchange-coupled bilayer nanodots consisting of a soft magnetic Ni81Fe19 (permalloy; Py) layer and a perpendicularly magnetized L10-FePt layer by measuring the polar magneto-optical Kerr effect (MOKE). A MOKE system having a 2-μm-diameter laser spot was used, which detected the signal from around 20 nanodots of 200 nm in diameter. The measured polar MOKE loops exhibited a two-step behavior attributable to each magnetization reversal process of the Py and L10-FePt layers, allowing us to evaluate the switching field (Hsw) of L10-FePt from the MOKE loop. Under the application of both a static magnetic field and an rf magnetic field (hrf), the nanodots showed a clear Hsw reduction with characteristic hrf frequency dependence. This Hsw reduction is well interpreted as a behavior of spin wave-assisted magnetization switching. We also discuss the influence of the Py layer thickness on spin wave-assisted Hsw reduction.

AB - We investigated the magnetization switching behavior of exchange-coupled bilayer nanodots consisting of a soft magnetic Ni81Fe19 (permalloy; Py) layer and a perpendicularly magnetized L10-FePt layer by measuring the polar magneto-optical Kerr effect (MOKE). A MOKE system having a 2-μm-diameter laser spot was used, which detected the signal from around 20 nanodots of 200 nm in diameter. The measured polar MOKE loops exhibited a two-step behavior attributable to each magnetization reversal process of the Py and L10-FePt layers, allowing us to evaluate the switching field (Hsw) of L10-FePt from the MOKE loop. Under the application of both a static magnetic field and an rf magnetic field (hrf), the nanodots showed a clear Hsw reduction with characteristic hrf frequency dependence. This Hsw reduction is well interpreted as a behavior of spin wave-assisted magnetization switching. We also discuss the influence of the Py layer thickness on spin wave-assisted Hsw reduction.

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Magnetization switching behavior of exchange-coupled bilayer nanodots characterized by magneto-optical Kerr effect

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