A new magnetometer for small scale magnetic studies

Abstract

A new magnetometer is described for measurement of the permanent magnetization of small particles of magnetic material and for the examination of magnetized surfaces. It has been developed for investigations in rock magnetism involving small grains of natural magnetic minerals, both after separation from the parent rock and while still in place in a rock surface. The detector is a small spherical magnet on one end of a fine, horizontal glass arm, the other end of which is attached to a vertical torsional suspension. A torque is produced about the suspension axis when the magnet is in a horizontal magnetic field with a vertical gradient, such as is produced by a magnetized particle in the vicinity of the magnet. Particle magnetizations of the order of 10^-9 G cm³ (10^-12 A m²) may be measured, and, under appropriate conditions, estimates of low field susceptibility of the particles may also be made.