A sensitive method of Hall measurement

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Abstract
A novel system is described for measuring very small Hall voltages by reversing the magnetic field with a time period of 1 s or more. The current is supplied from a direct constant current source and the system has a limit of sensitivity at 0.1 mu V Hall signal measured in a sample of total resistance 5.6 M Omega with a field of 0.5 Wb m-2 and a current of 10 mu A. The apparatus described has been used to measure mobilities of 10-3 cm2 V-1 s-1 in amorphous Ge films. The method described does not utilize very expensive equipment or special magnets and there are no calibration problems or difficulties in determining conductivity type. Utilization magnetoresistance and Nernst thermomagnetic effects are discussed.