The magnetoresistance (MR) oscillations in Mg have been systematically investigated. The small-amplitude MR oscillations have been recorded simultaneously with the de Haas-van Alphen (dHvA) oscillations as a function of magnetic field, field orientation, and temperature. Several new experimental problems peculiar to small-amplitude MR oscillation work in metals are discussed in detail. A theoretical analysis of the experimental deviations from the predictions of current Shubnikov-de Haas (SdH) theory is given. It is found that when magnetic breakdown causes deviation from the normal MR field dependence, it also causes deviation from the present SdH theory. Five basic mechanisms for MR oscillation are discussed, the SdH and four non-SdH mechanisms. Because magnesium is already well understood, and because the dHvA oscillations provided a reliable basis for interpretation of the data, the MR oscillations could be sorted out and classified in terms of the basic mechanisms.
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