2001 Fiscal Year Final Research Report Summary
Self assembled nanoscale structure - super sensitive tunneling magnetoresisitance effect of dielectric and ferromagnetic hybrid structure
| Project/Area Number |
12650311
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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 | Toyohashi University of Technology |
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Principal Investigator |
INOUE Mitsuteru Toyohashi University of Technology, 工学部, 助教授 (90159997)
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| Project Period (FY) |
2000 – 2001
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| Keywords | tunneling magnetoresistance effect / obliquely sputtering / nanoscale magnetic structure / granular ferromagnetic film / multi layered film / permalloy film |
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| Research Abstract |
Granular magnetic composite films, in which nano-scale ferromagnetic metal particles such as Co are dispersed in insulator matrices such as Sm_20_3, are attractive materials for electronic applications, because the extra degrees of freedom (e. g. granule size and metal volume fraction) of films enable us to fabricate tailored media for applications. Especially, the large tunneling-type magnetoresistance (TMR) effect that these films exhibit is useful for constructing magnetic heads and sensors for various electronic applications ; magnetically soft TMR effect of films becomes indispensable. In this report, we demonstrate that the low field response of the resistivity change of Co-Sm-0 films can be improved considerably by employing FeNi obliquely sputtered films as the underlayer of the granular films.
Films were prepared by using a rf-magnetron sputtering apparatus. The substrate was placed on a copper wedge with inclination angle θ=60deg fixed to the cathode. Ferromagnetic thin films
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(Fe, Co, Ni and Fe_<20>Ni_<80>) with nano-scale structures were formed by RF magnetron sputtering under oblique cathode arrangements. The oblique sputtering was effective to form self-organizing like nano-scale corrugate structures whose average height and spacing were approximately 10 nm. The resultant films clearly exhibited uniaxial inplane magnetic anisotropy due to the shape effect, but the magnitude and the direction of easy axis changed from sample to sample depending strongly on the material and the film thickness (deposition time). Beside the shape effect, crystalline magnetic anisotropy also plays an important role for the formation of uniaxial anisotropy of the nano-scale magnetic structures.
An underlayer of composted film used an obliquely sputtered FeNi films were subject to post ion-milling etching. Then, The Co_<76>(Sm_20_3)_<24> (f_v=52vol.%) granular film with 43 nm thickness was directly deposited onto the FeNi obliquely sputter deposited film with the average thickness of 20 nm. The composite film exhibited a considerably soft magnetization due to the stray field in gaps between neighboring FeNi nano-scale corrugate structures. The magnetic softening of film yielded the improvement of low field TMR response : with a small field of 500e, the Δp/p_0(p_0=2.9X10^5μΩcm) value of film reached more than 3 %. From this value, the field sensitivity of Δp/p_o of the composite film is evaluated to be about 240 times higher than that of the Co-Sm-0 single-layer film, suggesting the effectiveness of the obliquely sputtered FeNi underlayer film. Less
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