A high precision method for the pressure dependence in the de Haas-van Alphen effect

During the last decade studies of the pressure dependence of the Fermi surface cross-sectional areas in metals from the changes in the de Haas-van Alphen (dHvA) frequency have provided valuable information on lattice potentials. Because of the relatively small compressibility of metals, however, the changes in lattice constants with applied pressure and hence the resulting changes in Fermi surface dimensions are small and demand a high precision in the frequency measurement. A method has therefore been developed which greatly enhances the accuracy with which dHvA frequencies in a complex signal can be determined. The principle of the method is that all frequencies generated in the sample under investigation are measured in units of a reference dHvA frequency, which is provided by a second sample; this reference sample should generate not more than one dHvA frequency in the range of field of interest. The method has been used in a field modulation apparatus incorporating a 7.5 Tesla high homogeneity superconducting magnet. (Auth.)