Perpendicular-field r.f. surface impedance of indium

Abstract

This paper reports the analysis of experiments on the r.f. surface impednace of thin slabs of single crystal indium in the presence of a d.c. magnetic field normal to the slab plane. While our experimental results are generally in agreement with thos of Krylov, we diverge on their interpretation. Our analysis is based on a calculated Fermi surface model and on numerical calculations of dispersion relations and the surface impedance. We find for the (001) sample plane a weak Doppler-shifted cyclotron resonance (DSCR) absorption in the propagating helicon regime which provides a sensitive test of the model Fermi surface. For the helicon absorption edges corresponding to relatively strong DSCR absorption, the calculated dispersion and surface impedance results for the edge are compared with experimental results for the (001), (100), (111) and (110) sample planes. For the (001) and (110) planes we also observe oscillations in the DSCR absorption regime which are almost periodic in the applied d.c. field. Our surface impedance calculations indicate that these are not Gantmakher-Kaner oscillations but that they correspond to weak DSCR modes with a circular polarization sense opposite to that of the helicons.