Recent advances in the thin-film inductance-variation magnetometer

A coil coupled to the hard axis of a thin magnetic film, or group of films, exhibits an inductance which is dependent on the easy-axis static field. A simple and effective magnetometer can be constructed using two such transducers, with opposing film magnetization senses, in a self-excited balanced configuration. The circuit requires very low operating power and, with the addition of magnetic feedback, is capable of resolving field changes on the order of 10
^-6
Oe. The resolution is limited by film-generated noise and extends to smaller field changes as the planar areas of the films are increased. Magnetometers have been constructed using films ranging from 6 mm square to 16 mm square.