ANISOTROPY OF MAGNETIC HYSTERESIS PROPERTIES OF AUDIO-TAPE SAMPLES : ITS APPLICATION FOR THE MAGNETIC ANISOTROPY OF GNEISSIC ROCKS
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概要
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The magnetic anisotropy of hysteresis properties of audio-tape samples which were made from single domain (SD) of γ-hematite were measured using a vibration sample magnetometer (VSM). Subsequently after alternating field demagnetization (AF demagnetization) of natural remanent magnetization (NRM) up to 60mT, the anhysteretic remanent magnetization (ARM) was produced by applying an external alternating field up to 120mT under the geomagnetic field in the laboratory. After these ARM acquisitions, these ARMs were demagnetized by AF field up to 70mT. On the hysteresis properties of audio-tape, H_C (coercivity) and I_R (saturation isothermal remanent magnetization) were found to be more anisotropic than χ_<diff> (differential susceptibility at low field); these anisotropic maximum axes were parallel to the length of the tape. The anisotropic maximum axis of χ_<diff> was perpendicular to that of I_R and H_C in the tape plane. The most stable remanent magnetization after AF demagnetization remained parallel to the maximum axis of H_C and of I_R. On the basis of the similarity of the magnetic properties between the tape sample and the gneissic rocks from the Skarvsnes area, East Antarctica, it is clear that SD alignment in rocks shows the perpendicular anisotropic maximum axis of χ_<diff> to that of I_R and H_C. Therefore, this anti-phase of the anisotropy may be an important index to determine SD alignment in metamorphic rocks. The present study suggests that the NRM from old rocks not always shows the ancient geomagnetic field.
- 国立極地研究所の論文
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関連論文
- THE MAGNETIC ANISOTROPY OF GNEISSIC ROCKS FROM THE SKARVSNES AREA, EAST ANTARCTICA
- ROCKMAGNETIC ANALYSIS OF SEDIMENTARY SEQUENCES FOR PALEO-ENVIRONMENTAL RESEARCH
- ANISOTROPY OF MAGNETIC HYSTERESIS PROPERTIES OF AUDIO-TAPE SAMPLES : ITS APPLICATION FOR THE MAGNETIC ANISOTROPY OF GNEISSIC ROCKS