2002 Fiscal Year Final Research Report Summary
Synthesis of Granular Layers by Ion Implantation and the GMR Properties
| Project/Area Number |
13650355
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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 | Kurume Institute of Technology (2002)
Hosei University (2001) |
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Principal Investigator |
HAYASHI Nobuyuki Kurume Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (30318612)
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| Co-Investigator(Kenkyū-buntansha) |
TORIYAMA Tamotsu Musashi Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (40016176)
SAKAMOTO Isao National Institute of Technology, Tsukuba Center, Senior Scientist, つくば中央, 主任研究員
HASUYAMA Hiroki Kurume Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (00037962)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Giant Magnetoresistance / Nanosized Clusters / Tunneling conduction / Superparamagnetism / Mossbauer spectroscopy / Nano-cluster of Fe-Co alloy |
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| Research Abstract |
Main results are summarized as follows:
1) Dose dependence of GMR effect and magnetoresistance (MR) ratio ;
In the Fe/Al_2O_3 granules synthesized by ion implantation the highest MR ratio is obtained as 7.5% at the dose of 1.5×10^<17> ions/cm^2, where the α iron clusters are observed to be in critical sizes to do a transition from superparamagnetic to ferromagnetic states. Thus, superparamagnetic nanoclusters dispersed in the insulating oxide.
2) Estimation of the size distribution in nano-sized Fe clusters ;
The size distribution was estimated from the analysis of conversion electron Mossbauer spectra and the magnetization measurements. At the dose of 1.5×10^<17> ions/cm^2 the radii of Fe are estimated to be in wide distribution with the two peak values of 2.1 nm and 4 nm.
3) Evolution of new TMR granules and treatment to improve TMR characteristics ;
Fe ions are implanted into single crystals of MgO and amorphous SiO_2 to investigate the possibility of synthesizing various GMR granules. However, it is found that the MR ratios for the both nanocomposites are about 1 % at most, in contrast to Fe/Al_2O_3. However, we have found that in the implanted layers the dispersion state is altered after annealing in N_2 atmosphere at such low temperature as 550 K, which leads to the improvement of GMR properties, e.g., the increase of MR ratio to 3.5 % in Fe/MgO.
5) Development of new type of alloy nanoclusters ;
We have succeeded in presenting an evidence that the clusters of Fe-Co alloys can be synthesized by sequential implantation of Fe and Co ions. It is expected that the syntheses of alloy clusters by the implantation develop new fields of material science and magnetism.
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