Minimizing sample shape and size effects in all purpose magnetometers.

ABSTRACT

When measurements are made with a magnetometer, it is usually assumed that the sample produces a pure dipolar magnetic field. This is only true if the sample is a sphere. If the sample is not a sphere, the magnetic field produced by it will also contain higher order multipoles. These components of the magnetic field depend not only on the volume and magnetization but also on the sample's shape and size. Ideally the measured moment of a sample is only proportional to the sample's magnetization and volume. This paper explains why a sample's shape and size affects the response of a magnetometer, shows results illustrating this effect, and discusses conditions that will minimize these effects.