Longitudinal Ultrasonic Attenuation in Tantalum at Frequencies up to 1 GHz

Abstract

The attenuation due to interaction with conduction electrons of longitudinal sound propagating along [110] in a Ta crystal of resistance ratio 390 has been measured over the frequency range 0.46 to 1.0 GHz. The product of the wave vector q and the electronic mean free path l determined from the frequency dependence of the normal state attenuation ranges over 1.8 < ql < 3.8. The attenuation in the superconducting state in the absence of a magnetic field fits the BCS expression for 1.2 < T < Tc = 4.46 K with 2Δ(0) = 3.62 ± 0.06 kTc. The ultrasonic waves have been generated by thin film CdS transducers, and the conversion efficiency has been found to vary inversely with the active area of the transducer.