2006 Fiscal Year Final Research Report Summary
Measurements of magnetic properties of natural rock-forming minerals under pressure
| Project/Area Number |
17540398
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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 |
Solid earth and planetary physics
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| Research Institution | Kochi University |
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Principal Investigator |
KODAMA Kazuto Kochi University, Center for Advanced Marine Core Research, Professor, 海洋コア総合研究センター, 教授 (00153560)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIOKA Takashi Kochi University, Dept of Material Science, Faculty of Science, Professor, 理学部, 教授 (10218117)
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| Project Period (FY) |
2005 – 2006
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| Keywords | AC susceptibility / ferromagnetic mineral / pressure / temperature / magnetite / Curie temperature |
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| Research Abstract |
We have aimed to conduct a laboratory experiment for measuring alternating-current (AC) magnetic susceptibility and its temperature dependence under pressure around one GPa. For this purpose, we have developed a small, c. 70mm long, devise that consists of primary and secondary coils for measuring mutual inductance, a heater coil and a thermocouple, all of which are molded with heat-resistive cement. Then, the coil system is placed within a laboratory-made piston cylinder that can give rise to hydrostatic pressure by means of a handy, uni-axial press. We have carried out a series of experiments for characterizing magnetic behaviors of the coil system at an atmospheric pressure. We have used Nickel as a test sample and succeeded in measuring magnetic susceptibility change with temperature, whereby detecting a ferromagnetic phase transition with Tc equivalent to that of Nickel (631K). Then, we have measured fragments of a natural volcanic rock that contains pure magnetite as a sole magnetic carrier. We could detect Tc of magnetite (853K). These results show that the new coil system would be useful for not only detecting Tc, but also investigating changes in AC magnetic susceptibility with frequency. The latter could provide a new means for estimating grain size as well as identifying magnetic minerals in natural rocks. We finally carried out a series of experiments using Nickel by pressurizing at c. 10 MPa. The results appear to be successful, reproducing Tc of Nickel, but also show it still hard to make precise measurements of AC susceptibility under pressure. We should point out that a solid media should be used as a pressure transmitter, instead of BN powder used in this study, in order to avoid break-down of the coil system caused by the greater volume change of BN with the more pressurized.
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