Electron Relaxation Time from Magnetoacoustic Oscillations and the Tilt Effect

Several ultrasonic techniques for measuring electron relaxation time τ in a metal or semimetal are described. Two methods involve the variation in the peak-to-peak attenuation of geometric resonance oscillations in a decreasing magnetic field. The third involves attenuation peaks in the tilt effect, and the fourth involves the low-field disappearance of Landau-level oscillations in the tilt effect. The methods were applied to data taken in Bi at an ultrasonic frequency of 9.3 GHz. For the directions studied in our sample, ωₛτ ranged from 0.175 to 0.30. It is suggested that the first method can be applied to existing magnetoacoustic data.