2019 Fiscal Year Research-status Report
Design and development of spin-torque-oscillator and recording media for microwave assisted magnetic recording
| Project/Area Number |
19K05257
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
S.Amin Hossein 国立研究開発法人物質・材料研究機構, 磁性・スピントロニクス材料研究拠点, 主幹研究員 (10621758)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | Spin Torque Oscillator / Magnetic Recording / spin accumulation / spin polarization / granular media |
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| Outline of Annual Research Achievements |
Microwave assisted magnetic recording (MAMR) is a promising technology to overcome the stagnated areal density increase of hard disk drives. However, its most essential part, “spin-torque-oscillator (STO)”, has not been realized.
We numerically demonstrated the potential of the all-in-plane STO, which composes in-plane magnetized spin-injection layer (SIL) and field-generating layer (FGL) for MAMR. We found the magnetization direction of SIL can be switched to the opposite direction to that of applied external magnetic field by use of spin-transfer-torque that results in oscillation of FGL with a large cone angle at a reduced J. We designed SIL to reduce the critical current density, J_cr, required for the magnetization switching of SIL. The materials with a smaller Ms and spin polarization (β) in SIL results in reduction of Jcr and enables STO to oscillate with frequency of above 20 GHz with a large out-of-plane oscillation cone angle. The validity of this finding was studied experimentally. Based on this, we developed STO with Ni80Fe20 as SIL and Fe67Co33 as FGL experimentally. The oscillation begavior of SIL and FGL was fully addressed in this work. This work demonstrate the merit of realizing OPP mode oscillation with a simple and thin structure suitable for a narrow gap recording head. In particular, we realized STO oscillating with OPP mode with a FGL cone angle of 70o. We have also investigated development of novel FePt-media media with a nano-granular structure for the next generation of recording technology.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
By employing advanced micromagnetic simulations, we successfully designed required materials for SIL and FGL that can result in development of desired STO device for MAMR. We have developed this device experimentally and currently fully understood its oscillation mechanism. In the remaining two years of the project, the further optimization and development of STO will be carried out. In addition, we have successfully carried out fundamental studies on the novel media materials with nano-granular structure and small in-plane component of magnetization for the next generation of recording technology as planned in the proposal.
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| Strategy for Future Research Activity |
In the remaining time of the project, we will focus on design of FGL in all-in-plane STO device which was not done yet. we will develop STO for MAMR write head that produces a large Hac, uniform oscillation with a tunable frequency at a range of 20-40 GHz using small bias current density J<1.0×1012 A/m2. The designed STO will be developed experimentally and its oscillation behavior will be analyzed. Using aberration corrected STEM, the multilayer and interface structures of STO will be evaluated.We will also design and development of new media material and corresponding STO characteristics required for magnetic recording using MAMR for areal densities>2Tb/in2 using advanced MAMR recording simulations. The significance of this research proposal and its originality is its unique combinatory fundamental research approach; advanced numerical studies, experimental development of device, and nanostructure characterizations that will enable us to demonstrate STO and media materials for MAMR, the next generation of magnetic recording with areal density>2Tb/in2.
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| Causes of Carryover |
Due to the Coronavirus outbreak, a planned conference (IEEE Advances in Magnetics) in Italy in March 2020 was postponed to the next Fiscal year. Hence, part of the budget for attending this conference is transferred to the next Fiscal year. In addition, due to the COVID-19, I needed to reschedule part of the experiment plans and purchase of related goods related to the development and analysis of STO device to the next Fiscal year. Hence, part of the related budget is transferred to the next Fiscal year accordingly.
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