2002 Fiscal Year Final Research Report Summary
Controls of spin dependent tunneling in 2-dimensional granular magnetic films and development of active devices
| Project/Area Number |
12650314
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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 | Shimane University |
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Principal Investigator |
HONDA Shigeo Shimane University, Interdisciplinary Faculty of Science and Engineering, Professor, 総合理工学部, 教授 (00034405)
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| Co-Investigator(Kenkyū-buntansha) |
NAWATE Masahiko Shimane University, Interdisciplinary Faculty of Science and Engineering, Associate Professor, 総合理工学部, 助教授 (10198400)
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| Project Period (FY) |
2000 – 2002
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| Keywords | granular films / low dimensional array / tunneling magnetoresistance / extraordinary Hall effect / ferromagnetic semiconductor / Coulomb blockade / porous Si / ion implantation |
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| Research Abstract |
1. Film thickness dependence of magnetization and magnetoresistance in Fe-SiO2 granular films.
The saturation magnetization increases with thickness, and a step behavior appears at around 200 nm in the thickness dependence of the magnetization and transport properties. These behaviors are explained by a model of double-layered structure; the first layer near the substrate having smaller magnetization and the second layer with larger magnetization. These magnetic and transport properties is explained by a model, in which the formation of non-magnetic shell is enhanced near the substrates. These structure was confirmed by X-ray photoelectron spectroscopy.
2. Tunneling magnetoresistance in low-dimensional Co-SiO2 films.
(1) The tunneling giant magnetoresistance properties have been examined for ultrathin Co-SiO_2 granular films, forming the pseudo 2-dimensional alignment of Co granules. In the 35 vol.%-Co films of 5 and 10 nm thickness, the magnetoresistance (MR) ratio increased with reducin
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g temperature similar to thick films. On the other hand, in the 28 and 32 vol.%-Co films thinner than 5 nm, the MR ratio decreased drastically below 100K with reducing temperature reflecting the 2-dimensional alignment of Co granules.
(2) Samples of CPP (current perpendicular to plane) structure with narrow current pin-holes, AuCr/SiO_2/Co-SiO_2/SiO_2/AuCr, exhibited the non-linearity in current to voltage (I-V) relation, suggesting that the tunneling barrier tunneling probabilities of majority or minority spin band relating to the variation of E.
3. Magnetic and transport properties of alternately deposited Co-Bi films.
Both ordinary magnetoresistance (OMR) and anisotropic magnetoresistance (AMR) are observed in Co-Bi films. The OMR component, for which the Bi matrix is responsible, decreases with increasing Co volume fraction x, while the AMR component, due to Co, increases. For x = 17, the spontaneous Hall resistivity indicates strong temperature dependence. With the increase of temperature, polarity switches at 150 K from negative to positive. At room temperature Hall Resistivity or Hall coefficient shows a larger value than pure Co bulk by 2 orders of magnitude.
4. Extraordinary Hall effect in Co implanted GaAs hybrid magnetic semiconductors.
Hybrid Co/GaAs ferromagnetic semiconductors have been prepared by implantation method. In these samples, sheet resistance shows weak temperature dependence, and the extraordinary Hall effect with positive coefficient is observed. In small Co content samples, Hall resistance increases with decreasing temperature and maximum value of 3.6 x 10-2 Ω is obtained at 150 K. Less
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Research Products
(11 results)
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[Publications] S,Puwanto., I,Sakamoto., M,Koike., H,Tanoue., S,Honda.: "Effects of ion irradiation on Structural and magnetic properties of Fe/Si multilayers prepared by helicon plasma sputtering"Nuclear Instruments and Methods in Physics Research B, to appear. (2003)
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