Magnetic moments of fine particles from micromagnetic surveys

Abstract

A new scanning magnetic microscope to image magnetic fields with micrometric resolution has been constructed based on a giant magnetoresistance (GMR) sensor. Operating in zerofield, the GMR sensor is sensitive to the components of the magnetic field arising from the remanent magnetisation parallel to the plane of the cut rock surface. The field component perpendicular to the surface therefore has to be calculated using FFT relationships. The spatial resolution of the system is 20 µm, and its peak-to-peak noise during operation is 250 nT. Its high spatial resolution and a minimum sensor- to-sample distance of only 30 µm compensate for its rather modest field sensitivity.