Abstract
The magnetic field dependence in the amplitude of de Haas-van Alphen or magnetoresistance oscillations introduces magnetic field dependent phase shifts which are not included in the standard formation of the Lifshitz-Kosevich theory. It is found that the magnetic field dependence of the oscillatory amplitude introduces an additional signal which is pi /2 out of phase in 1/H with respect to the signal which would be observed if the amplitude of the oscillation is strictly independent of magnetic field strength. A number of examples are presented which illustrate the magnitude of this magnetic field dependent amplitude effect when the large amplitude modulation field technique is employed to measure the frequency of the quantum oscillations.