ABSTRACT

Sound transmission experiments on single‐crystal and polycrystalline nickel and iron samples 10–20 μm thick demonstrate an amplitude dependence on conductivity indicative of an electron damping effect. The samples form part of the common wall between two microwave cavities. Transverse sound waves were generated via magnetostriction with a static magnetic field perpendicular to the sample surface and perpendicular to the incident microwave magnetic field. Longitudinal sound waves were generated by direct electromagnetic excitation with a static magnetic field parallel to the sample surface and parallel to the incident microwave magnetic field. An exponential dependence of transmitted sound amplitude versus sample conductivity was observed as the temperature was varied. This exponential amplitude dependence on conductivity is what is expected from theories for sound wave attenuation in metals. For our samples this attenuation coefficient is of the order of 0.5 dB/μm. At low temperatures, where the product of the sound propagation constant and the electron mean free path approaches and exceeds unity, a decrease in the sound amplitude dependence on conductivity was observed, also in agreement with theory.