Ultrasonic attenuation was studied in pure In, In + 0.003 at.% Pb, pure Pb and Pb + 0.003 at.% In in the intermediate states (for the magnetic fields 0.7Hc and 0.9Hc) and superconducting states, for frequencies varying from 9.9 to 29.7 MHz, in the temperature range 4.2 to 1.4K. Collective excitation modes were observed in both the states for all the samples. There exist two distinct phases in the intermediate state but only one phase in the superconducting state in all the samples. The first phase was dependent on the magnetic field and independent of the concentration and nature of the dopant. The second phase was independent of the magnetic field and dependent essentially on the concentration of vacancies and marginally on the concentration of the dopant. The origin of the two phases has been discussed.
Volume 94, 2020
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