2021 Fiscal Year Research-status Report
Laser-induced deterministic magnetization switching for next-generation magnetic recording
| Project/Area Number |
21K14521
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| Research Institution | National Institute of Advanced Industrial Science and Technology |
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Principal Investigator |
王 建 国立研究開発法人産業技術総合研究所, 材料・化学領域, 研究員 (80792069)
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| Project Period (FY) |
2021-04-01 – 2023-03-31
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| Keywords | エネルギーアシスト磁化反転 / 光誘起磁化反転 / 熱流スピン流変換 / 超高密度磁気記録 / FePt媒体 |
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| Outline of Annual Research Achievements |
The goal of this research project is to develop a novel magnetic recording technique by realizing laser-induced deterministic magnetization switching in magnetically hard FePt nanogranular film. For this purpose, we explored the interconversion between heat (phononic), light (photonic), and spin (spintronic) for ultrafast manipulation of magnetization reversal in an yttrium iron garnet (YIG) substrate/FePt-C nanogranular film heterostructure. In the first year (FY 2021), we successfully established perpendicular magnetic anisotropy (PMA) in a 6-nm-thick FePt-C nanogranular film magnetron sputtered on a YIG (111) single crystal substrate. The magnetization loop of the films shows a squareness (Mr/Ms) about 0.72 and a perpendicular coercivity about 6.62 kOe which is comparable to the film deposited on MgO (100) substrate with identical condition. With such promising preliminary results, we further performed the all-optical helicity-dependent switching measurement on such films deposited both on MgO (100) ang YIG (111) single crystal substrates. It is interesting to find that compared with MgO substrate, the laser induced magnetization switching of FePt-C nanogranular film on YIG substrate shows a clear enhancement (~50%) both on the intensity and helicity-depended switching. The results unprecedently proved the substantial contribution of thermal gradient induced spin-transfer torque (STT) on the magnetization switching in hard FePt nanogranular media. Up-to-now a related scientific journal paper is accepted.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
According to the research plan, first year (FY2021) of this research has been dedicated mainly on materials platform design and evaluation that can enable the study of role of thermal gradient induced spin-transfer torque (STT) on the magnetization switching in hard FePt nanogranular media. Although the temporary teleworks associated to the COVID-19 brought some difficulty in the experiment progress, the research target for the first year is now completed. We are working on proof experiment by further optimization and/or double check of the results. We have started microstructure characterization of the samples as well. We are now also writing the manuscripts for publication and planning to present part of the results in the coming international and domestic conferences.
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| Strategy for Future Research Activity |
In FY2022, we will firstly be working on the proof experiments including substrate dependence (YIG vs. GGG vs. STO substrate) and laser power dependence of thermal gradient induced spin-transfer torque (STT) on the magnetization switching in hard FePt nanogranular media. Then, we will go further for the related mechanism study associated with detailed microstructure analysis to quantify the relationship. Finally, we will try to utilize the hint and/or knowhow from the mechanism study to feedback the materials and/or microstructure design in order to achieve the final target “laser-induced deterministic magnetization switching in magnetically hard FePt nanogranular film”. The results will be presented in international conference (MMM 2022) as well as domestic conferences in Japan and scientific journal papers will be published out of the obtained results.
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| Causes of Carryover |
Due to the Government of Japan declared state of emergency in relation to the novel coronavirus disease (COVID-19) in FY2021, some of the collaboration research/visiting experiments were canceled and/or postponed. Thus, the planned budget for the business trips and accommodation were not executed.
In FY2022, the incurring amount of budget will be mainly used for business trips and accommodations for the visiting experiments and for attending the related international and domestic conferences to present/share all the results obtained from this research project to the society.
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