Differential method for Hall-coefficient measurements in an a.c. magnetic field

A compensation method for Hall-coefficient measurements with an audiofrequency magnetic field and a direct sample current is described. An a.c. magnetic field is generated in a ferritecored coil working in a series-resonance circuit.1 Compensation is achieved over a wide frequency range of the magnetic field by the use of RC bridges and a differential amplifier. The method eliminates spurious e.m.f.s and after small modifications permits the (pulsed) changes of Hall coefficient to be measured with high sensitivity.