| Project/Area Number |
13355026
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Structural/Functional materials
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
INOMATA Koichiro Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (90323071)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Yoshiaki Research and Developed Center, Toshiba Corporation, Senior Researcher, 研究開発センター・記憶材料デバイスラボ, 主任研究員(研究職)
TEZUKA Nobuki Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (40323076)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥51,740,000 (Direct Cost: ¥39,800,000、Indirect Cost: ¥11,940,000)
Fiscal Year 2002: ¥11,570,000 (Direct Cost: ¥8,900,000、Indirect Cost: ¥2,670,000)
Fiscal Year 2001: ¥40,170,000 (Direct Cost: ¥30,900,000、Indirect Cost: ¥9,270,000)
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| Keywords | MRAM / spin switching / synthetic antiferromagnetic coupled film / MFM / tunnel magnetoresistance / annealing / MRAM / スピントンネル接合 / 微細加工 / 磁気抵抗効果 |
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| Research Abstract |
Magnetic random access memory (MRAM) using TMR memory cells possesses the attractive properties of non-volatility, radiation hardness, nondestructive readout, low voltage, high access time, unlimited read and write endurance and high density. The TMR, however, significantly decreases with increasing bias voltage, which leads to reduction of the signal voltage for the actual MRAM. A ferromagnetic double tunneling junction (DTJ) was proposed for the high density MRAM application. It was demonstrated that a large signal voltage over 100 mV can be obtained using DTJ because of the smaller degradation of the TMR for the bias voltage, which is significantly higher than 30 mV of the conventional single junctions.
The arrays of the synthetic antiferromagnetic (SyAF) patterned bits consisting of Co_<90>Fe_<10>(t_1 nm)/Ru(d nm)/Co_<90>Fe_<10>(t_2 nm) were successfully fabricated with micron to submicron sizes and different aspect ratios. Magnetization switching field H_<sw> and magnetic domain st
… More
ructure were investigated using magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM), respectively. It was demonstrated that the strongly AF-coupled SyAF with aspect ratio k = 1 creates size-independent H_<sw> down to submicron sizes fabricated, which is understood by zero demagnetization field for k = 1 and single domain structure observed by MFM. The size-independent switching field demonstrates the predominance of the SyAF for ultra high bit density MRAMs, requiring a low switching field and stabilized single domain. The size-independent spin switching field was also observed in magnetic tunnel junctions (MTJs) using a SyAF free layer consisting of Co_<90>Fe_<10> (t_1) / Ru (0.5 nm) / Co_<90>Fe_<10>(t_2) , which was deposited on a thermal oxidized Si substrate using an ultrahigh vacuum sputtering system, and patterned using an electron beam lithography and Ar ion milling into micron to submicron sizes. A SyAF free layer can keep high remanence even for the aspect ratio of 1, and exhibits the size-independent spin switching field in all element widths from 16 to 0.25 μm investigated. Additionally, the MTJs using a SyAF free layer consisting of Co_<90>Fe_<10> (3 nm) /Ru (0.5 nm) / Co_<90>Fe_<10> (1.5 nm) show a TMR ratio 40% after annealing at 250℃. These results demonstrate that a SyAF free layer is an available structure for spin-electronics nano-devices including MRAMs. Less
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