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On the origin of apparently negative minimum susceptibility of hematite single crystals calculated from low-field anisotropy of magnetic susceptibility
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SYSNO ASEP 0546387 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title On the origin of apparently negative minimum susceptibility of hematite single crystals calculated from low-field anisotropy of magnetic susceptibility Author(s) Hrouda, F. (CZ)
Ježek, J. (CZ)
Chadima, Martin (GLU-S) RID, SAISource Title Geophysical Journal International - ISSN 0956-540X
Roč. 224, č. 3 (2021), s. 1905-1917Number of pages 13 s. Publication form Print - P Language eng - English Country GB - United Kingdom Keywords Magnetic properties ; Magnetic fabrics and anisotropy ; Magnetic mineralogy and petrology ; Rock and mineral magnetism OECD category Condensed matter physics (including formerly solid state physics, supercond.) Method of publishing Limited access Institutional support GLU-S - RVO:67985831 UT WOS 000606573600026 EID SCOPUS 85099616092 DOI 10.1093/gji/ggaa546 Annotation As shown in the literature several times, the calculation of the anisotropy of magnetic susceptibility (AMS) of hematite single crystals using standard linear AMS theory reveals that the calculated minimum principal susceptibility is parallel to the crystallographic c-axis, but is negative, which is however not due to diamagnetism as evidenced by direct measurements of susceptibility along the principal directions. Susceptibility of a few hematite single crystals from Minas Gerais, Brazil, was measured in 320 directions using a special 3-D rotator and the measurements were processed through AMS calculation by means of standard linear theory and through constructing contour diagrams in equal-area projection. In addition, the susceptibility was in detail measured in three perpendicular planes approximately passing through the main crystallographic directions. The crystals show extremely high anisotropy, the susceptibility measured along the basal plane is several hundred times higher than that along the c-axis and the AMS ellipsoids are very oblate. The contour diagrams show relatively simple patterns of directional susceptibilities, similar to those of the second-rank tensor. Fitting tensor to measured hematite grains results in small but negative minimum principal susceptibility. Nevertheless, summation ofmany oriented grains filters out the non-tensorial parts of the grain susceptibility in multicrystal assemblages, the AMS of which is well represented by a tensor. Workplace Institute of Geology Contact Jana Popelková, popelkova@gli.cas.cz, Sabina Janíčková, Tel.: 233 087 272 Year of Publishing 2022 Electronic address https://academic.oup.com/gji/article-abstract/224/3/1905/5989708
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