New Methods for De Haas-Shubnikov Measurements

Improved techniques and instrumentation for observing the de Haas-Shubnikov (dHS) effect are described and preliminary results of their application to measurements on bismuth are presented. The two main features of the method are: first, the monotonic H
²
term in the magnetoresistance is subtracted out, allowing increased amplification of the oscillatory part, and therefore increased sensitivity in detecting the periods; second, the magnetic field is swept such that 1/H varies linearly in time, producing dHS oscillations sinusoidal in time, making it possible to use real-time differentiation and filtering to separate interfering periods. The method thus provides a large amount of data reduction prior to recording, permits direct measurement and averaging of the periods from the recorded data, and allows a more accurate and unambiguous interpretation of the data. Much of the instrumentation described (1/H sweep, filter, differentiator) has been built around commercially available operational amplifiers.