| Project/Area Number |
11650320
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Japan Advanced Institute of Science and Technology |
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Principal Investigator |
GOMI Manabu School of Materials Science, Japan Advanced Institute of Science and Technology Associate Professor, 材料科学研究科, 助教授 (80126276)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Keywords | Spin Tunneling Junction / Magnetic Oxide Thin Film / Giant Magnetoresistance / Pulsed Laser Deposition / Magnetite Thin Film / Surface Magnetism / Low Temperature Growth / Half-Metallic Oxide Ferromagnet / トンネル磁気抵抗 / 反位相境界 / パルスレーザ堆積 / ダブルプロブスカイト酸化物 |
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| Research Abstract |
Optimum fabrication conditions of the junctions and influence of surface magnetic of the ferromagnetic oxides on tunneling magnetoresistance have been investigated in order to achieve large magnetoresistance effect in tunneling junctions using transition metal oxides with half metallic nature. The results are summarized as follows :
1.Thin films of Fe_3O_4 and MgO with high quality were grown by pulsed laser deposition (PLD) at low temperature. The insulating MgO layer was required to be grown at lower temperature than 200℃ even at oxigen pressure of 1 x 10^<-5> Torr in order to prevent the Fe_3O_4 surface from oxidizing in a fabrication process of junction. Thin films of Sr_2FeMoO_6 with half metallic nature which is a promising candidate of ferromagnetic electrode were successfully grown at 500℃, lower than the reported growth temperature.
2.Optimum PLD-growth conditions for MgO insulating layers were determined. Analysis of current-voltage characteristics of Fe_3O_4/MgO/Au junction structures fabricated under the optimum conditions showed that the junctions with MgO insulating layer as thin as 1 nm have good tunneling quality.
3.Tunneling magnetoresistane (TMR) due to the magnetization of the Fe_3O_4 electrodes aligned in anti-parallel was observed in a Co_<0.4>Fe_<2.6>O_4/Fe_3O_4/MgO/Fe_3O_4 junction, though the TMR change was as low as -0.5 %. The magnetic field dependence of TMR showed that the low TMR may be associated with the superparamagnetic behavior of the surface magnetization of Fe_3O_4 electrode layers.
4.The Fe_3O_4/NiO/MgO/NiO/Fe_3O_4 junction structures with double insulating layers of non-magnetic MgO - magnetic NiO were fabricated. However, the expected junction properties were not obtained due to some issues caused by large junction area and NiO layers as thin as 1 nm. The advanced process fabricating the fine structure such as photolithography will be required to overcome these problems.
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