2007 Fiscal Year Final Research Report Summary
Development of Magnetic Materials for High-frequency Region by the Formation of Ferrite Nano-rod Array
| Project/Area Number |
17350088
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional materials/Devices
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| Research Institution | Gunma University |
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Principal Investigator |
HANAYA Minoru Gunma University, Graduate School of Engineering, Professor (50228516)
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| Co-Investigator(Kenkyū-buntansha) |
SAKURAI Hiroshi Gunma University, Graduate School of Engineering, Associate Professor (80251122)
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| Project Period (FY) |
2005 – 2007
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| Keywords | ferrite / thin film / nano rod / sputtering / magnetic property / magnetic permeability / magnetic anisotropy / high-freauency region |
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| Research Abstract |
Ferrite materials have been widely used as various electronic devices in relatively high-frequency region up to a few hundreds of MHz, because of high magnetic permeability and high-electrical resistivity. The decrease of the magnetic permeability in the high-frequency region is explained as Snoek's limit, and the Snoek's limit is known to be brought to higher frequencies by the introduction of magnetic anisotropy to the ferrite. In this work, we tried to develop magnetic materials for high-frequency region of GHz order by introducing magnetic anisotropies to ferrites by controlling their bulk shapes to thin films and to nano-rod arrays. The results are as follows: (1) We prepared NiZn ferrite (Ni_<0.5> Zn_<0.5> Fe_2O_4) and NiZnCu ferrite (Ni_<0.2> Zn_<0.6> Cu_<0.2> Fe_2O_4) thin films by rf magnetron sputtering with employing quartz glass plates as substrates, and tried to control the crystalline size by the change of the substrate temperatures during the sputtering. The crystalline size was developed successfully from less than 10 nm to about 40 nm with the increase of the substrate temperature from 200 to 700℃, and the formed nano-crystalline thin film samples exhibited the extension of high-frequency limit in the permeability to a few GHz. (2) NiZn ferrite nano-rod arrays were formed successfully by rf magnetron sputtering of the ferrite onto nano-porous alumina membranes. The formation of the ferrite nano rods with the diameter of 〜 200 nm and the length of 〜 1 μm were confirmed by SEM observations to be achieved through the accumulation of the sputtered ferrite clusters on the alumina membrane with reflecting the surface structure of the membrane. The magnetic anisotropy was observed in the ferrite nano-rod arrays, and the samples exhibited high magnetic permeability even in the frequency region of GHz order.
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