Magnetization Hysteresis Loop Tracer for Long Specimens of Extremely Small Cross Section

Abstract

An instrument for measurement of the low frequency magnetic properties of thin layers is described. The difference signal from two opposed pick-up coils, one of which contains the sample, is amplified, integrated, and amplified again to cause the vertical deflection of a cathode-ray oscillograph to be proportional to the intensity of magnetization of the specimen. A signal is applied to the horizontal deflecting plates of the oscillograph to cause it to represent the applied magnetizing field in the region of the pick-up coils. A large reduction in low frequency noise in the difference signal preamplifier is accomplished by use of a circuit similar to electrometer tube circuits. Noise introduced through integration of sharp peaked signals is reduced by use of first and third harmonic components in the magnetizing field current. A signal equal to noise is produced by a flux change of 75×10−6 maxwell.