Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil.
Department of Geophysics, Observatório Nacional, Rio de Janeiro 20921-400, Brazil.
Sensors (Basel). 2019 Apr 5;19(7):1636. doi: 10.3390/s19071636.
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/(Hz) in an unshielded environment. The magnetic moment sensitivity is 1.3 × 10 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.
我们改进了一种磁扫描显微镜，用于在地质样品的薄片中以亚毫米尺度测量矿物的磁性。该显微镜由一个 200 微米直径的霍尔传感器组成，该传感器距离样品 142 微米；一个能够在 40 毫米直径的区域内对样品施加高达 500 mT 直流磁场的电磁铁；一个以梯度配置布置的第二霍尔传感器，用于抵消电磁铁施加的背景信号并降低系统的整体噪声；一个定制的电子系统，用于偏置传感器并允许调整背景信号消除；以及一个具有微米分辨率的扫描 XY 工作台。在未屏蔽的环境中，我们的系统在 6.0 Hz 时实现了 200 微米的空间分辨率和 300 nT/（Hz）的噪声水平。磁矩灵敏度为 1.3 × 10 Am²。我们使用考虑了样品几何形状的替代模型成功测量了地质样品的代表性磁化强度，并在样品薄片中识别出不同的微观特征。
