Characterizing complex mineral structures in thin sections of geological samples with a scanning hall effect microscope

• 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 nT rms /(Hz) 1/2 in an unshielded environment. The magnetic moment sensitivity is 1.3 × 10 −11 Am 2 . 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.

Nyckelord

Geological sample

Hall sensor

Magnetic materials

Magnetic scanning microscope

Electromagnets

Geology

Hall effect transducers

Magnetic moments

Scanning

Background signals

DC magnetic field

Electronics system

Geological samples

Spatial resolution

Unshielded environment

Microscopes

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