2004 Fiscal Year Final Research Report Summary
Modeling an oblique anhysteretic remanent magnetization using low-temperature and alternating-field demagnetizations.
| Project/Area Number |
15540407
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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 | Tokyo Institute of Technology |
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Principal Investigator |
TSUNAKAWA Hideo Tokyo Institute of Technology, Graduate School of Science and Engineering, Professor, 大学院・理工学研究科, 教授 (40163852)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Paleomagnetism / Rock magnetism / Anhysteretic remanent magnetization / Thermoremanent magnetization / Single-domain particle / Multi-domain particle / Coercivity force / Low-temperature demagnetization |
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| Research Abstract |
Anhysteretic remanent magnetization(ARM) is normally imparted applying a dc field parallel to alternating field(AF), that is ‘parallel ARM'. In this study we have experimentally investigated oblique ARM(OARM) which is given under the condition of a dc field oblique to or perpendicular to AF. We have modeled its acquisition mechanism and suggest its application to the paleomagnetic study. The results obtained in this study will be summarized as follows.
(1)Device for parallel, perpendicular and oblique ARMs
Orthogonality of two-axis dc fields for OARM is better than 0.5 deg.
Linearity of dc field intensity vs. current is confirmed with very high precision.
(2)Measurement of bulk OARM
OARM intensity is linearly acquired with applied dc fields in range of 10-100 micro T.
Intensity :
Parallel ARM>Oblique ARM>Perpendicular ARM
Addivity law of OARM :
OARM(AF;DC1,DC2;Hc1,Hc2)=OARM(AF;DC1,0;Hc1,Hc2)+OARM(AF;0,DC2;Hc1,Hc2) DC1:Dc field by Coil-1,DC2:Dc field by Coil-2,He:coercivity force
Uni-axis AF demagnetization curve is almost the reverse of ARM acquisition curve.
Low temperature demagnetization(LTD) :
LTD components (multi-domain particle origin) show a direction parallel to the applied dc field.
LT memory (single-and pseudo-single-domain particle origin) does not show a parallel direction.
(3)Modeling OARM acquisition
It is suggested that the observed characteristics of OARM can be explained with the shape-anisotropy model of SD particles and the domain-wall model of MD particles.
(4)Application of OARM
It is thought that OARM has a potential for evaluation of SD, PSD and MD components.
OARM can be used in the LTD-DHT Shaw method in the absolute paleointensity determination.
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