Low-field extremum in the surface impedance of metals at MHz frequencies

The first detailed measurements of the low-field extremum for a cylindrical sample at MHz frequencies are reported. It is shown that the model suggested by Sibbald et al. is the only interpretation of the low-field extremum which can account either for the measurements reported here or those carried out for similar extrema observed in flat samples. The theoretical basis for this interpretation is investigated, and the importance of Fermi surface geometry is given special emphasis.