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

(2019) J. Araujo, André L. A. Reis, Vanderlei C. Oliveira Jr., A. F. Santos, C. Luz-Lima, E. Yokoyama, L. A. F. Mendoza, J. M. B Pereira, A. C. Bruno


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Araujo, J., A. L. A. Reis, V. C. Oliveira Jr., A. F. Santos, C. Luz-Lima, E. Yokoyama, L. A. F. Mendoza, J. M. B. Pereira and A. C. Bruno (2019). Characterizing Complex Mineral Structures in Thin Sections of Geological Samples with a Scanning Hall Effect Microscope. Sensors, 19(7), 1636. doi: 10.3390/s19071636

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This paper is part of a scientific collaboration between Observatório Nacional and Pontifical Catholic University of Rio de Janeiro in scanning magnetic microscopy.

The peer-review at Sensors is open and can be found at Peer-Review Record.

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.