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Sensors 2019, 19(7), 1636; https://doi.org/10.3390/s19071636

Characterizing Complex Mineral Structures in Thin Sections of Geological Samples with a Scanning Hall Effect Microscope

1
Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil
2
Department of Geophysics, Observatório Nacional, Rio de Janeiro 20921-400, Brazil
3
Department of Physics, University of California, Santa Barbara, CA 93106, USA
4
Department of Physics, Campus Ministro Petrônio Portella, Universidade Federal do Piauí, Teresina 64049-550, PI, Brazil
5
Institute of Geosciences, University of Brasília, Brasília 70910-900, Brazil
6
Department of Electrical Engineering, Universidade Estadual do Rio de Janeiro, Rio de Janeiro 20550-900, Brazil
7
Fiber Optics, RISE Acreo, Electrum 236, 164 40 Kista, Sweden
*
Author to whom correspondence should be addressed.
Received: 13 March 2019 / Revised: 2 April 2019 / Accepted: 3 April 2019 / Published: 5 April 2019
(This article belongs to the Special Issue Magnetic Sensing Technology, Materials and Applications)
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Abstract

We improved a magnetic scanning microscope for measuring the magnetic properties of minerals in thin sections of geological samples at submillimeter scales. The microscope is comprised of a 200 µm diameter Hall sensor that is located at a distance of 142 µm from the sample; an electromagnet capable of applying up to 500 mT DC magnetic fields to the sample over a 40 mm diameter region; a second Hall sensor arranged in a gradiometric configuration to cancel the background signal applied by the electromagnet and reduce the overall noise in the system; a custom-designed electronics system to bias the sensors and allow adjustments to the background signal cancelation; and a scanning XY stage with micrometer resolution. Our system achieves a spatial resolution of 200 µm with a noise at 6.0 Hz of 300 nTrms/(Hz)1/2 in an unshielded environment. The magnetic moment sensitivity is 1.3 × 10−11 Am2. We successfully measured the representative magnetization of a geological sample using an alternative model that takes the sample geometry into account and identified different micrometric characteristics in the sample slice. View Full-Text
Keywords: magnetic scanning microscope; hall sensor; magnetic materials; geological sample magnetic scanning microscope; hall sensor; magnetic materials; geological sample
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Araujo, J.F.D.F.; Reis, A.L.A.; Oliveira, V.C., Jr.; Santos, A.F.; Luz-Lima, C.; Yokoyama, E.; Mendoza, L.A.F.; Pereira, J.M.B.; Bruno, A.C. Characterizing Complex Mineral Structures in Thin Sections of Geological Samples with a Scanning Hall Effect Microscope. Sensors 2019, 19, 1636.

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